Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Researchers, expension personnel and producers interested in biology or control of biting flies on animals. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? One undergraduate student and two graduate students have gained substantial experience working in these systems. How have the results been disseminated to communities of interest? Results have been presented at the Livestock Insect Workers' Conference, Society for Vector Ecology, and the national meeting of the Entomological Society of America. What do you plan to do during the next reporting period to accomplish the goals? We will complete writing of applicable papers and present updates on research at meeting of the Livestock Insect Workers' Conference and Entomological Society of America.
Impacts
What was accomplished under these goals?
Experiments were completed documenting the ability of C. sonorensis eggs to survive extreme desiccation. Field experiments were completed testing midge responses to different types of traps in the field, and how that impacted bluetongue virus infection levels in the midges collected. Other trials were completed examining how horn flies and face flies used cattle dung pats in the field (versus pat size) and how the seasonal abundance reflected diapause at this very southern latitude. The egg and 4 stages of the larvae of C. sonorensis were described morphologically.
Publications
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Progress 10/01/09 to 09/30/14
Outputs
Target Audience:Rearchers, extension personnel, and producers interested in ecology and control of biting flies affecting livestock Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?One Ph.D. student has worked on Culicoides egg desiccation tolerance and larval/pupal freezing tolerance. One undergraduate student has worked on Culicoides egg distribution in the field, and another worked on horn fly utilization of cattle dung pats and interactions with the other pest fly in those pats, the face fly Musca autumnalis (two publicaiotns in preparation). These students learned a lot about how to conduct research and how to push it forward to publication. How have the results been disseminated to communities of interest?Yes, we have presented a number of scientific papers at meetings, including the Livestock Insect Workers' Conference, Society for Vector Ecology, and the Entomological Society of America. These mainly reach researchers and academic-based extension personnel. We also have spoken with 4H groups about horn fly biology and control and involved several other undergraduates in helping with different aspects of the research. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Trials were conducted 2010-2012 to evaluate fatty acids and geraniol as horn fly repellents in the field on cattle. Those trials were completed successfully and the first publication is being prepared. Using C. sonorensis as a model, trials were conducted and a paper published using eggs to determine how resistant they are to desiccation. Current trials are examining how cold-tolerant the immature stages are, whether preconditioning with exposure to above-freezing temperatures can protect them against freezing, and how we might measure that (methods development). We also are studying field distribution of Culicoides eggs relative to waterline in wastewater ponds.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
McDermott, E. G. and B. A. Mullens. 2014. Desiccation tolerance in the eggs of the primary North American bluetongue virus vector, Culicoides sonorensis (Diptera: Ceratopogonidae), and implications for vector persistence. J. Med. Entomol. 51: 1151-1158.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Osborne, C. J., C. E. Mayo, B. A. Mullens, E. G. McDermott, A. C. Gerry, W. K. Reisen and N. J. MacLachlan. Lack of evidence for laboratory and natural vertical transmission of bluetongue virus in Culicoides sonorensis (Diptera: Ceratopogonidae). J. Med. Entomol. 52: 274-277.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Researchers, extension agents, and producers interested in ecology and control of biting flies and associated disease agents to livestock. Changes/Problems: The many laboratory assays to support the field colelcting and repellent testing effort required more time than expected to execute, but now have been completed. With the discovery of the new fly (face fly), we also added that to our repellent work. What opportunities for training and professional development has the project provided? Several undergraduate and graduate students have been able to help periodically with the project and thus learn a lot about how to sample and visually estimate flies on cattle, how to assess cattle defensive behaviors, and how to process captured flies to determine levels of blood ingestion, fly age, and mating and fecundity status. How have the results been disseminated to communities of interest? We ahve talked about these studies at several meetings. What do you plan to do during the next reporting period to accomplish the goals? We are analyzing and writing up the horn and face fly repellent studies, which are very detailed and long-term field efforts (3 yrs). We also are beginning to focus again on biting midges attacking cattle, which transmit bluetongue virus.
Impacts
What was accomplished under these goals?
We found face flies on southern California cattle, which were unexpected and cause irritation and transmit the disease agenyt of pinkeye. We documented their abundance and levels of parasitism with a parasitic nematode that parasitically castrates them. They also were included in repellent trials as a fly target (along with horn flies). Those studies have eben successfully completed and are being analysed before publication.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Soto, D., F. E. Fowler, B. A. Sandelin and B. A. Mullens.2014. Musca autumnalis (Diptera: Muscidae) and the host-specific nematode Paraiotonchium autumnale (Tylenchida: Iotonchiidae) in southern California. J. Med. Entomol. 51: 288-292.
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: There is an ongoing UCR-UC Davis collaborative project on biting midge (Culicoides sonorensis) vectors of bluetongue virus, centered mainly at UC Davis. This project focuses on vector field ecology on confinement dairies in the Central Valley, with the most recent, intensive adult midge trapping on one dairy at specific distances from a wastewater pond source. Some of these studies were recently published. The Davis postdoc came to UCR in summer 2012 to learn methods of immature midge monitoring, and planning meetings were held at UC Davis in spring 2012 to develop vector data useful for population and disease modeling. This year we have launched two new midge biology studies, being done by an MS and a PhD Entomology student. One will focus on the 4 larval stages of C. sonorensis, examining head capsule structures related to feeding abilities and preferences on different potential food items as the larvae age. The other is examining the phenomenon of egg dehydration, and whether it may be involved in environmental persistence. PARTICIPANTS: C. Mayo and N. J. MacLachlan from the UC Davis School of Veterinary Medicine; A. Gerry from UC Riverside Entomology. TARGET AUDIENCES: Researchers interested in vector-borne diseases, especially blue tongue. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The work with UC Davis has shown a distinct relationship between entomological risk (vector index involving virus presence and actual animal biting rates) and bluetongue virus transmission to sentinel cattle. It also showed that some California dairies lack sufficient numbers of vectors to sustain virus transmission. This work demonstrated similarities between midges biting cattle and those attracted to suction traps baited only with the host cue carbon dioxide. In contrast, midges collected from suction traps that used both carbon dioxide and ultraviolet light had somewhat different seasonal activity data. There were also differences in virus levels in vectors taken at light, relative to midges taken from cattle or traps with only carbon dioxide. This is a subject for future work, but has very high importance for interpreting light trap insect data in an epidemiological context. The UCR studies on midge immatures are very relevant as well. If we can understand how larvae feed, and what their preferences and requirements are, we may be able to manipulate larval habitats to be less favorable for the vectors. Similarly, knowledge of Culicoides egg stages is almost nonexistent. How midges and associated viruses overwinter is a very key epidemiological question. If desiccated eggs can endure long periods of unfavorable conditions, it could be important in explaining how the vectors persist spatially and temporally.
Publications
- Mayo, C. E., I. A. Gardner, B. A. Mullens, C. M. Barker, A. C. Gerry, A. J. Guthrie, and N. J. MacLachlan. 2012. Anthropogenic and meterorological factors influence vector abundance and prevalence of bluetongue virus infection of dairy cattle in California. Vet. Microbiol. 155: 158-164.
- Mayo, C. E., B. A. Mullens, A. C. Gerry, C. M. Barker, P. P. C. Mertens, S. Maan, N. Maan, I. A. Gardner, A. J. Guthrie and N. J. MacLachlan. 2012. The combination of abundance and infection rates of Culicoides sonorensis estimates risk of subsequent bluetongue virus infection of sentinel cattle on California dairy farms. Vet. Parasitol. 187: 295-301.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Two subprojects are included here. One involves Culicoides midges. In that project we have colonized the main western USA bluetongue vector, C. sonorensis. The second aspect is horn fly biology and responses to repellents. Extensive field data collection in CA involved two technicians and six undergraduates, with consequent training for them. Similar intensity summer data collection in the field has occurred in North Carolina. Two technicians and two undergraduates likewise have been involved in laboratory data collection from processing field samples, with another training aspect. In each summer we have involved multiple students from Cal Poly Pomona and NC State as well. This project just finished its second year. The nature of the intense field study is that each year is a replication. So, no disseminations are planned until the entire data set is complete. PARTICIPANTS: Principal participants for the Culicoides work were Drs. Bradley Mullens (UC Riverside Entomology) and Yuval Gottlieb (Hebrew University in Rehovot, Israel). Main technical assistance was from A. Diniz (UCR) and Y. Saroyan (Hebrew Univ.). The horn fly aspects included Drs. Bradley Mullens and D. Wes Watson (NC State Entomology). Partners included Cal Poly Pomona (particularly Dr. Broc Sandelin, Animal Science) and the Goldsboro Ag. Center (Goldsboro, NC). Technical assistance was provided by D. Soto, D. Tenney, A. Diniz, C. Martin, F. Fowler and A. Murillo. TARGET AUDIENCES: Veterinary entomologists (research, extension and industry) and pastured cattle producers (beef and milk) are the main target audiences. In the course of the study we have presented the project goals and taught aspects of the methods to students in Israel, California and North Carolina. PROJECT MODIFICATIONS: Both projects are proceeding as planned. Due to differences in cattle herd availability, California horn fly trials are occurring in two periods of 6 weeks each. North Carolina trials are occurring using both repellents simultaneously over a 9 week period. Fifty male and fifty female horn flies per collection date, site and assay resulted in excessive lab effort, so that number was reduced to 30 with little loss in data resolution.
Impacts
This project has involved extensive methods development and training. For the Culicoides project we designed a rearing system with water paddle agitators and an artificial blood-feeding apparatus. Specifically for horn flies we have developed methods to grind the insects (testing different grinding bead sizes, composition, tube designs and times) appropriately to allow body processing for hemoglobin quantification, and head grinding for pterin measurement. Specific dissection techniques include ovarian dissection for fecundity measurements and egg development stages, as well as spermatheca removal for mating assessment. Specific field animal behavior techniques include developing definitions and sampling methods for animal defensive behaviors against flies.
Publications
- No publications reported this period
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Some work with Culicoides species has continued this year, specifically a survey of these biting midges at the San Diego Wild Animal Park and completion of a paper from the 2008 research in Spain. We also are continuing work on novel repellents for biting flies on cattle, specifically geraniol and fatty acids. We ahve published results of two studies on the field biology of the human nuisance pest fly, Fannia conspicua. PARTICIPANTS: UC Riverside undergraduate student Dale Halbritter helped with the Culicoides survey, and the canyon fly work was done primarily by UC Riverside MS student Rachel Mohr (Alec Gerry, major professor). The horn fly repellent work is being done with the direct help of UC Riverside extension specialist Alec Gerry, technician Diane Soto and Cal Poly Pomona undergraduate Diana Tenney. The key collaborator at Cal Poly Pomona is associate professor Broc Sandelin, and high school agriculture teachers Gary Hunt and Phil Pacia are important at Sonora High School, where other cattle horn fly populations are being studied. TARGET AUDIENCES: Personnel at California Vector Control Districts should be interested in the canyon fly work. Medical entomologists, wildlife biologists and parasitology researchers should be interested in the Culicoides work. Agricultural and industry scientists/researchers and producers should be interested in the horn fly work. PROJECT MODIFICATIONS: No major modifications.
Impacts
The San Diego Wild Animal Park has a diverse Culicoides fauna, dominated by members of the cactus-dwelling guild (C. cacticola and others), C. cockerellii group, and C. sonorensis. The survey is now completed and hopefully will be written up this year, with emphasis on species that may be transmitting pathogens such as arboviruses or Haemoproteus to their animals. Deltamethrin was tested on sheep in Spain for its effectiveness in preventing Culicoides biting using enclosure traps, and the material completely prevented biting for at least 4 days. Fatty acids (C8-9-10) are excellent short-term protectants against feeding on cattle by stable and horn flies. We have a 3-year study now entering its second year, and in collaboration with North Carolina State Univ. This is testing fatty acids and geraniol for impacts on horn fly population biology. Trials on canyon flies, a human nuisance pest, were published, showing how important sugar feeding is for both sexes and the attraction of ammonia, which has implications for improved monitoring or management of the adults.
Publications
- Mohr, R. M., B. A. Mullens and A. C. Gerry. 2011. Diel patterns of female host-seeking, male swarming, and sugar feeding in the "canyon fly", Fannia conspicua (Diptera: Muscidae) in southern California. J. Med. Entomol. (in press).
- Mohr, R. M., B. A. Mullens and A. C. Gerry. 2011. Evaluation of ammonia, human sweat, and bovine blood as attractants for female "canyon fly", Fannia conspicua (Diptera: Muscidae), in southern California. J. Vector Ecol. (in press).
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Three research areas are included in this project. One is ecology of biting midge (Culicoides spp.) vectors of bluetongue (BTV) and epizootic hemorrhagic disease viruses (EHDV), the second is biology of canyon flies (Fannia conspicua and related forms), and the third is biology and control of biting flies on large animals such as cattle (mainly Stomoxys calcitrans and Haematobia irritans). Studies at the San Diego Wild Animal Park and San Diego Zoo have documented the Culicoides fauna there and allowed us to propose some suspects for transmission of avian malaria (Haemoproteus spp.) and ruminant viruses such as BTV and EHDV. Culicoides spp. developing in rotten cactus are abundant in spring and likely suspect for bird malaria, while C. sonorensis is abundant along polluted waterways in the park and probably are transmitting the ruminant viruses. Another new project (funded by BARD) with Israel aims to examine microbial symbionts of Culicoides that may be influential in governing vector competence. In summer 2009 a study of canyon flies was done in La Habra Heights (Los Angeles Co.) to examine survival and distribution of adults via pterin analyses and mark-release-recapture. The adults are both rather focal and quite long-lived. Finally, we are launching a new horn fly project (funded by USDA-CAR) to study population-level responses to use of geraniol and fatty acids for density reduction, reducing biting and host irritation, and reducing mating success or survival. We now are developing the techniques based on dissection and pterin analysis. PARTICIPANTS: The Culicoides work is being done in collaboration with Dr. Simon Anthony of the San Diego Zoological Society and involves Dale Halbritter, an undergraduate Entomology major at UCR and Dr. Alec Gerry of UCR. The symbiont work is being done in collaboration with Dr. Yuval Gottlieb at Hebrew University near Tel Aviv and Kim Hung, a UCR Ph.D. student. The canyon fly work involves Diane Soto, research technician at UCR, Dr. Gerry, and Alesha Diniz, and undergraduate Biology major at UCR. The horn fly project is being done in collaboration with Dr. D. Wes Watson at North Carolina State University and Dr. Jerry Zhu at the USDA-ARS laboratory in Lincoln, Nebraska. TARGET AUDIENCES: Target audiences are researchers and extension personnel in veterinary and medical entomology, zoo health professionals, California residents bothered by canyon flies in coastal mountain communities, and cattlemen concerned with horn fly impact and suppression. PROJECT MODIFICATIONS: We periodically add new studies which fit the area, as with the canyon fly studies and horn fly work.
Impacts
We now can focus on certain suspect species for pathogen transmission at the San Diego Wild Animal Park, including efforts to identify pathogens from field-collected insects. Knowing where the midges are developing may allow us to reduce their numbers by habitat management. Canyon fly results suggest that local adult fly management by toxic baits etc. has promise. Recently published work with the fatty acids on several muscoid fly species sets the stage for intensive field trials on horn fly control. In general, the support for these projects has clearly been used very productively and is leveraging other, more robust funding at the federal level.
Publications
- Gerry, A. C., V. Sarto I Monteys, J.-O. Moreno Vidal, O. Francino and B. A. Mullens. 2009. Biting Rates of Culicoides Midges (Diptera: Ceratopogonidae) on Sheep in Northeastern Spain in Relation to Midge Capture using UV Light and Carbon Dioxide Baited Traps. J. Med. Entomol. 46: 615-624. 66.
- Mullens, B. A., A. C. Gerry, V. Sarto i Monteys, M. Pinna and A. Gonzalez. 2010. Field Studies on Culicoides (Diptera: Ceratopogonidae) Activity and Response to Deltamethrin Applications to Sheep in Northeastern Spain. J. Med. Entomol. 47: 106-110.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: A worldwide review of mermithid nematode parasitism of biting midges was completed and published. Studies were begun on biting midges (Culicoides spp) collected from the San Diego Wild Animal Park near Escondido, using a variety of traps. The species in the area are now being determined, and we hope to document seasonal activity in preparation for more detailed studies on species of particular interest for animal pathogen transmission there. A field test of fatty acids potentially useful in repelling biting flies from cattle was conducted in 2008. Stable fly numbers were reduced by about 50-80% on dairy heifers treated on day=0, with some smaller effects possibly persisting through about day 3 post-treatment. A paper on laboratory repellency assays of the fatty acid mixtures against stable flies, horn flies, and house flies was completed. This should set the stage for further work with the fatty acids in the field against horn flies, which were quite sensitive in laboratory bioassays. PARTICIPANTS: Drs. Sarto (Catalonia, Spain) and Przhboro (St. Petersburg, Russia) were critical in reviewing some of the worldwide mermithid nematode literature. Dr. Simon Anthony (San Diego Wild Animal Park) and Dr. Alec Gerry (UCR Entomology) are involved in the Culicoides survey. Dr. William Reifenrath (Stratacor, Inc.) and Dr. Sarah Butler (UCR Ph.D. student) were involved in the fatty acid work. TARGET AUDIENCES: Target audiences are extension personnel, farmers, and scientists interested in improving animal production. PROJECT MODIFICATIONS: There have been no major project modifications.
Impacts
Mermithid nematodes are key natural enemies of biting midges that transmit disease agents, and thus may be useful for biological control. Traditional insecticidal materials are being lost for livestock use due to resistance development and societal concerns, so nontoxic repellents for livestock flies are critically needed, especially for milking cattle and for organic systems. The fatty acids are promising and have extremely low toxicity.
Publications
- Mullens, B. A., Sarto I Monteys, V. and Przhboro, A. A. 2008. Mermithid parasitism in the Ceratopogonidae: A literature review and critical assessment of host impact and potential for biological control. Russian Entomol. J. 17: 87-113.
- Mullens, B. A., W. R. Reifenrath and S. M. Butler. 2009. Laboratory trials of fatty acids as repellents or antifeedants against house flies, horn flies, and stable flies (Diptera: Muscidae). Pest Mgmt. Sci. (in press).
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Additional laboratory trials were conducted on a nontoxic repellent against biting flies comprised of fatty acids. In the laboratory the material had good activity against horn flies in a Petri dish bioassay featuring treated and untreated surfaces available for resting flies. The minimum statistically significant active level was 0.06 mg per square cm in the laboratory bioassay, which is less than 20% of the intended field application rate of a dust formulation. This is promising for field applications against that pest, and another test against stable flies is planned for spring 2008. The material might be useful if applied frequently even to lactating cows.
PARTICIPANTS: Professional training includes participation by Sarah Butler, recent Ph.D. from my laboratory. Collaborators include Dr. Alec Gerry, UCR Entomology and Mr. Nyles Peterson, UC Cooperative Extension Farm Advisor (Dairy).
TARGET AUDIENCES: Applied researchers, farmers, cooperative extension personnel
Impacts
The laboratory and field trials are an early attempt to develop nontoxic repellents for use on milking cows, on which almost no pesticides can be used due to concern for milk residues. The materials also have potential for use on other animals such as horses.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
Laboratory and field trials were conducted on a nontoxic repellent against biting flies comprised of fatty acids. In the laboratory the material had good activity against horn flies in a Petri dish bioassay featuring treated and untreated surfaces available for resting flies. The minimum statistically significant active level was 0.06 mg per square cm in the laboratory bioassay, which is less than 20% of the intended field application rate of a dust formulation. This is promising for field applications against that pest. A field trial was conducted against stable flies in the field using a mineral oil formulation. Although fly numbers were marginal for such a test, short-term control was good, and the material might be useful if applied frequently even to lactating cows.
Impacts
The laboratory and field trials are an early attempt to develop nontoxic repellents for use on milking cows, on which almost no pesticides can be used due to concern for milk residues. The materials also have potential for use on other animals such as horses.
Publications
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Progress 01/01/05 to 12/31/05
Outputs
Stable fly adult activity during the spring activity period was related to seasonal rainfall patterns on dairies for 5 years. Late (March) rains were related to stable fly activity 2 fly generations later. For each cm of March rainfall, the biting activity increased about 1 fly per leg count. The appearance of high stable fly numbers can be estimated by the degree days (above a 10 degree C baseline) accumulated since these late spring rains. Stable flies greatly influence cattle fly defensive behaviors, which are strongly related to fly abundance. Individual cattle maintain their ranks (relative to other cows in the herd) with regard to fly numbers, and relative ranks for each of the defensive behaviors were even more consistent. In other words, there are cows that are irritable and inherently carry fewer flies, and others that are less so. The first direct field evidence for habituation to fly biting pain was recorded in these trials; a given number of flies early in
the season causes more intense reactions (and possibly result in more damage) than the same number later in the year. For these reasons, monitoring behaviors may be superior (and possibly easier) than monitoring the flies themselves. Finally, a trial was conducted using a new, nontoxic repellent against stable flies in the field. Short-term control was good, and the material might be used if applied frequently even to milking cows.
Impacts
Impact: Approximating future stable fly abundance as a function of rainfall allows producers to take extra action against future fly problems. For example, in a wet year they can estimate when problem numbers will occur and have about 2 months to remove manure etc. to reduce the problem. The cow behavior-stable fly study is a very important paper, in that it proposes using behaviors rather than fly loads per se and shows clearly how different individual animals are in their reaction (and habituation) to fly biting. The field trial is an early attempt to develop nontoxic repellents for use on milking cows, on which almost no pesticides can be used due to concern for milk residues.
Publications
- Publications: Mullens, B. A. and N. G. Peterson. 2005. Relationship between rainfall and stable fly ((Diptera: Muscidae) abundance on California dairies. J. Med. Entomol. 42: 705-708.
- Mullens, B. A., K.-S. Lii, Y. Mao, J. A. Meyer, N. G. Peterson and C. E. Szijj. 2006. Behavioural responses of dairy cattle to the stable fly, Stomoxys calcitrans, in an open field environment. Med. Vet. Entomol. 20: 122-137.
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Progress 01/01/04 to 12/31/04
Outputs
Culicoides and other biting flies possibly related to horse dermatitis were studied on the Palos Verdes Peninsula of Los Angeles County. Six midge species and several mosquito species were recovered either from carbon-dioxide-baited suction traps or from horses. The primary suspects are C. obsoletus and C. sonorensis. The mosquito Culiseta incidens also may be involved. All feed on the belly region of horses where the dermatitis lesions are mostly found, and are present in winter and spring, when the lesions begin to show up. The seasonality of obsoletus and its known ability to cause this condition make it a prime suspect. While mammal-feeding Culicoides normally are well sampled using these traps, C. obsoletus is much more common on horses than in traps, and the basis of this needs to be determined. Stable fly adult activity during the spring activity period was related to seasonal rainfall patterns on dairies for 5 years. Late (March) rains were related to stable
fly activity 2 fly generations later. For each cm of March rainfall, the biting activity increased about 1 fly per leg count.
Impacts
Knowing the likely cause of dermatitis yields possible solutions, such as stabling and fans to disrupt midge feeding, or appropriate insecticides/repellents applied to the belly or screens in a paddock area. We also need to determine the development sites of C. obsoletus to explore possible cultural control options (habitat management), as well as explore hyposensitization as a means of dermatitis relief. Approximating future stable fly abundance as a function of rainfall allows producers to take extra action against future fly problems.
Publications
- Mullens, B. A., J. P. Owen, D. E. Heft and R. V. Sobeck. 2005. Culicoides (Diptera: Ceratopogonidae) and other biting flies on the Palos Verdes peninsula of southern California, and their possible relationship to equine dermatitis. J. Amer. Mosq. Cont. Assoc. 21 (in press).
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Progress 01/01/03 to 12/31/03
Outputs
Culicoides and other biting flies possibly related to horse dermatitis were studied on the Palos Verdes Peninsula of Los Angeles County. Six midge species and several mosquito species were recovered either from carbon-dioxide-baited suction traps or from horses. The primary suspects are C. obsoletus and C. sonorensis. The mosquito Culiseta incidens also may be involved. All feed on the belly region of horses where the dermatitis lesions are mostly found, and are present in winter and spring, when the lesions begin to show up. The seasonality of obsoletus and its known ability to cause this condition make it a prime suspect. While mammal-feeding Culicoides normally are well sampled using these traps, C. obsoletus is much more common on horses than in traps, and the basis of this needs to be determined. Results are being prepared for publication.
Impacts
Knowing the likely cause allows us to propose solutions, such as stabling and fans to disrupt midge feeding, or appropriate insecticides/repellents applied to the belly or screens in a paddock area. We also need to determine the development sites of C. obsoletus to explore possible cultural control options (habitat management), as well as explore hyposensitization as a means of dermatitis relief.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Recent activity has focused on two Culicoides projects. First, we documented seasonal adult flight activity, size variability related to temperature, and parity in a salt marsh population of Culicoides occidentalis. This species was recently elevated to full species level but is closely related to C. sonorensis, the main vector of bluetongue virus. Adults of this population are active year-round, including high activity in winter. While body size was inversely related to air temperatures, greatly buffered temperature variability (coastal effect) resulted in far more stable body size relative to inland populations of both C. occidentalis and C. sonorensis. Parity was exceedingly low (<4%) and probably reflected poor host availability in this isolated habitat. Second, related to concerns about horse allergy, we are documenting activity of Culicoides on and near horses on the Palos Verdes Peninsula (Los Angeles Co.). Several species have been found, notably C. sonorensis
and C. freeborni (mainly summer and fall activity) and C. obsoletus (probably winter and spring activity). We will determine which are mainly biting horses, and hopefully the immature developmental sites.
Impacts
The biology of C. occidentalis is mostly unknown, but its relationship to the main bluetongue virus vector, C. sonorensis, makes it of particular interest. Knowing the Culicoides fauna near and biting horses, plus their developmental sites, is key to developing possible management strategies to reduce their biting rates and thus the allergy problems in horses.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
Our comprehensive field epidemiological studies and a study to determine if cattle could be protected against bluetongue via permethrin applications were published this year. Recent progress has been mostly in collaboration with N. J. MacLachlan and coworkers at the School of Veterinary Medicine, University of California, Davis. They characterized the NS3 and NS3A genes of bluetongue virus from field-collected vectors (Culicoides sonorensis) we obtained at an active transmission site. The virus exists as a heterogeneous population, rather than a single uniform type at a single site. A series of experiments was conducted using insects to transmit virus between sheep and cattle (more natural than syringe transmission). Individual virus gene segments evolved independently via genetic drift in a host-dependent fashion (quasispecies evolution). Direct evidence was found for a founder effect, in the form of a unique virus variant acquired by and fixed in the vector.
Finally, insects were only able to acquire virus and become infected when recoverable live virus was circulating in the ruminant; viral RNA detectable by PCR present over longer time frames did not indicate virus infectious for the vector.
Impacts
Studies provide the first direct evidence to suggest bluetongue virus may persist year-round in southern latitudes of the U.S. If proved, an "overwintering zone" for the pathogen might be defined and action taken to suppress the pathogen in this low phase of transmission
Publications
- Gerry, A. C., B. A. Mullens, N. J. MacLachlan and J. O. Mecham. 2001. Seasonal transmission of bluetongue virus by Culicoides sonorensis (Diptera: Ceratopogonidae) at a southern California dairy and evaluation of vectorial capacity as a predictor of bluetongue virus transmission. J. Med. Entomol. 38: 197-209.
- Bonneau, K. R., B. A. Mullens and N. J. MacLachlan. 2001. Genetic drift and "founder effect" of the VP2 and NS3/NS3A genes of bluetongue virus during passage between sheep, cattle and Culicoides sonorensis. J. Virol. 75: 8298-8305.
- Mullens, B. A., A. C. Gerry and R. K. Velten. 2001. Failure of a Permethrin Treatment Regime to Protect Cattle Against Bluetongue. J. Med. Entomol. 38: 760-762.
- Bonneau, K. R. J. B. Topol, A. C. Gerry, B. A. Mullens, R. K. Velten and N. J. MacLachlan. 2001. Variation in the NS3/NS3A gene of bluetongue viruses contained in Culicoides sonorensis collected from a single site in southern California. Virus Research (in press).
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Progress 01/02/00 to 12/31/00
Outputs
Analysis has been completed on a 3-year epidemiological study of bluetongue virus transmission to dairy cattle on a site in the Chino Basin of western San Bernardino Co., California. Virus transmission to sentinel calves occurred between August and November, but virus presence in CULICOIDES SONORENSIS was documented between May and December. Insects therefore were more sensitive than sentinel calves for detecting virus at this site. Infection rates in insects were 0.4%, and numbers collected and processed in winter were probably insufficient to detect a low level of infection. Winter survival was superior (>90%/day) and suggests a low-level virus transmission pattern may allow the virus to persist year-round. The best correlations between components of vector capacity and transmission were biting rates estimated from traps placed near the sentinel animals. A study of the biology of a close relative of C. SONORENSIS, C. OCCIDENTALIS, was begun at Bolsa Chica Marsh in
coastal Orange Co. Data to date suggest year-round activity, highest in late summer and fall.
Impacts
Studies provide the first direct evidence to suggest bluetongue virus may persist year-round in southern latitudes of the U.S. If proved, an "overwintering zone" for the pathogen might be defined and action taken to suppress the pathogen in this low phase of transmission
Publications
- No publications reported this period
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Progress 01/01/99 to 12/31/99
Outputs
Analysis has been completed on a 3-year epidemiological study of bluetongue virus transmission to dairy cattle on a site in the Chino Basin of western San Bernardino Co., California. Virus transmission to sentinel calves occurred between August and November, but virus presence in CULICOIDES SONORENSIS was documented between May and December. Insects therefore were more sensitive than sentinel calves for detecting virus at this site. Infection rates in insects were 0.5%, and numbers collected and processed in winter were probably insufficient to detect a low level of infection. Winter survival was superior (>90%/day) and suggests a low-level virus transmission pattern may allow the virus to persist year-round. The best correlations between components of vector capacity and transmission were biting rates estimated from traps placed near the sentinel animals.
Impacts
Studies provide the first direct evidence to suggest bluetongue virus may persist year-round in southern latitudes of the U.S. If proved, an "overwintering zone" for the pathogen might be defined and action taken to suppress the pathogen in this low phase of transmission.
Publications
- Gerry, A. C.and B. A. Mullens. 2000. Seasonal abundance and survivorship of Culicoides sonorensis (Diptera: Ceratopogonidae) at a southern California dairy, with reference to potential bluetongue virus transmission and persistence. J. Med. Entomol., accepted pending minor revision.
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Progress 01/01/98 to 12/01/98
Outputs
Two insecticides, permethrin and pirimiphos-methyl, were tested for utility in killing CULICOIDES VARIIPENNIS SONORENSIS and/or preventing blood feeding and transmission of bluetongue virus to cattle. Bioassays feeding laboratory-reared females through a thin hair layer from treated cattle in the field indicated that dorsal applications did not translocate to the belly (preferred feeding area) well enough to prevent feeding there. Permethrin was superior to pirimiphos-methyl in activity and persistence. Belly applications of permethrin to sentinel cattle reduced successful feeding (assessed by enclosure nets in the field) by over 85% for 7 days. However, field studies on seroconversion of permethrin-treated and untreated cattle herds to bluetongue indicated the pesticide did not prevent vector biting at levels sufficient to interrupt transmission.
Impacts
(N/A)
Publications
- MULLENS, B. A. and K. A. LUHRING. 1998. Age-dependent parasitism of Culicoides variipennis sonorensis (Diptera: Ceratopogonidae) be Heleidomermis magnapapula (Nematoda: Mermithidae) and considerations
- GERRY, A. C. and B. A. MULLENS. 1998. Response of male Culicoides variipennis sonorensis (Diptera: Ceratopogonidae) to carbon dioxide and observations of mating behavior on and near cattle. J. Med.
- MULLENS, B. A. and A. C. GERRY. 1998. Comparison of bait cattle and carbon dioxide-baited suction traps for collecting Culicoides variipennis sonorensis (Diptera: Ceratopogonidae) and Culex quinquefasciatus (Diptera: Culicidae). J. Med.
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Progress 01/01/96 to 12/30/96
Outputs
CULICOIDES VARIIPENNIS SONORENSIS larvae parasitized by HELEIDOMERMIS MAGNAPAPULA produce male nematodes when two or more parasites are present. Male size declines with parasite load. The fitness of males of various sizes is being assessed; extremely small males appear to be less capable of mating with females. In the field bluetongue virus is transmitted to dairy cattle only between late summer and mid-fall, despite large numbers of vectors earlier in the summer. Biting rates on cattle were strongly related to suction trap collections baited with carbon dioxide, but cattle are six to seven times as attractive to C.V. SONORENSIS relative to their equivalent carbon dioxide output. The mosquito CULEX QUINQUEFASCIATUS was attracted to cattle in exact proportion to its carbon dioxide output. Wild-collected CULICOIDES spp. fed in the laboratory more readily through chick skin membranes than through parafilm membranes. Vector competence of desert and dairy spp. is being
assessed for bluetongue virus.
Impacts
(N/A)
Publications
- VELTEN, R. K. and MULLENS, B. A. 1997. Field morphological variation and laboratory hybridization of CULICOIDES VARIIPENNIS SONORENSIS and C.V. OCCIDENTALIS (Diptera: Ceratopogonidae) in southern California. J. Med. Entomol.34 (in press).
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Progress 01/01/95 to 12/30/95
Outputs
A multi-year study began to track vector capacity of CULICOIDES VARIIPENNIS SONORENSIS parameters, determine virus frequency in field-collected flies, and relate them to bluetongue virus transmission to dairy calves. No transmission was detected until the September-December period, despite trap collections of over 5,000 females/trap/night in mid-late summer. Vectors are active year-round, but trap catches are less than 5/trap/night in winter. Morphological variation in the C. VARIIPENNIS complex was studied. Spicules on the male aedeagus are the only good character to separate C. V. OCCIDENTALIS from C. V. SONORENSIS. Characters commonly used to distinguish other spp. are not very useful for the forms in the complex. The forms hybridize in the lab and can be maintained indefinitely (at least through F7); hybrids sometimes exhibit intermediate spicule numbers. Desert CULICOIDES immature morphology studies should result in description of several unknown larvae/pupae and
two new spp. Eggs have chorion features which distinguish them and may yield clues to habitat and ecology.
Impacts
(N/A)
Publications
- No publications for this reporting period.
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Progress 01/01/94 to 12/30/94
Outputs
The mermithid nematode HELEIDOMERMIS MAGNAPAPULA is a parasite of CULICOIDES VARIIPENNIS, the main bluetongue vector in the U.S. Developmental rate curves are identical in slope to those of the host, with a lower threshold of 9-10 C for both organisms. Salt tolerance of the parasite probably limits its effectiveness in the field. Adult tolerances (24 hours) are 300-400 mM for NaCL and MgSO4; preparasites die at levels above 70 mM MgSO4 or 150 mM NaCL. Infectivity declines much faster than mobility and also is sensitive to salt level. Populations of C. V. SONORENSIS and C. V. OCCIDENTALIS were studied for morphological variability over a year. Features used to differentiate subspecies are seasonally variable and overlap too much to be very useful. Spines (or lack of them) on male genitalia were a good tool. The subspecies will hybridize and can be maintained in the lab; female hybrids cannot be separated from parental stocks, while males sometimes exhibit intermediate
numbers of genital spines. Desert CULICOIDES immature stages will be collected and associated with adults over the next 2 years; preliminary information indicates many can be reared on agar and nematodes. They also will be tested for susceptibility to nematode parasitism and bluetongue virus infection. A 3 year field epidemiology project on bluetongue also has been started on a local dairy.
Impacts
(N/A)
Publications
- No publications reported this period.
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