Progress 01/01/01 to 12/31/05
Outputs
All trichostrongylid nematodes, such as Ostertagia ostertagi, must undergo the exsheathment process before progressing to the first parasitic stage. Parasitism is prevented if exsheathment is prevented. This research furthers the understanding of the biological pathways involved in exsheathment so that new biological targets within these organisms for alternative control strategies may be identified. A small portion of a carbonic anhyrase (CA) gene from O. ostertagi has been isolated; this represents the first CA isolated from a parasitic nematode. Genomic characterization and quantitative expression of the O. ostertagi CA during the exsheathment process has been our focus. The primary hindrance to this work has been the propagation and recovery of infective larvae from the bovine host to obtain adequate amounts of genetic material from the parasites. We have successfully quantitated the expression of this enzyme during the exsheathment process and have made progress
in mapping the gene at the genomic level. To date, 2,000 bases of the promoter region have been sequenced as have the first two exons and first intron of the gene representing 2,500 bases. The temporal and quantitative expression of this gene is highly correlated with the temporal pattern of exsheathment. Some insight into the regulation of this gene has already been gained from current sequencing efforts. Further investigation will be necessary before an alternative approach to controlling gastrointestinal nematodes in cattle will be available to the cattle producer.
Impacts
The significance of this research is to understand the biology of parasitic nematodes with the overall objective of identifiying new biological targets within these organisms for alternative control strategies. The cattle industry is currently dependent upon one drug class (macrocyclic lactones) to effectively control gastrointestinal nematodes. If widespread resistance to this drug class occurs cattle producers suffer tremendous economic losses due to decreased growth performance. The economic effects of impaired reproductive and maternal performance due to gastrointestinal parasites is difficult to assess but will also severely impact capital gains of producers. Although the life cycles and developmental patterns of gastrointestinal nematodes have been well described, virtually nothing is known about the biology of these very economically important organisms. All trichostrongylid nematodes, such as O. ostertagi, must undergo the exsheathment process before
progressing to the first parasitic stage. Parasitism is prevented if exsheathment is prevented. The goal of this research is to understand the biological pathways involved in exsheathment inorder to define new targets for anthelmintic development so that an alternative approach to controlling gastronintestinal nematodes in cattle will be available to the cattle producer.
Publications
- Loyacano, A.F., Skogerboe, T.L., Williams, J.C., DeRosa, A., Gurie, J. and Shostrum, V.K. 2001. Effects of parenteral administration of doramectin or a combination of ivermectin and clorsulon on control of gastrointestinal nematode and liver fluke infections and on growth performance in cattle. J. Amer. Vet. Med. Assoc. 218:1465-1468.
- Loyacano, A.F., Williams, J.C., Gurie, J. and DeRosa. 2001. Effects of subclinical infections of internal parasites on the production of beef heifers. 2001 Beef Cattle Research Report (Vol. 31), LSU AgCenter, pp. 27-29.
- Williams, J.C. 2001. Stomach and intestinal worms. Parasitology Section, Beef Cattle Production in Louisiana. A handbook, Louisiana Cooperative Extension Service, LSU AgCenter, pp. 75-79.
- Williams, J.C. and Loyacano, A.F. 2001. Internal parasites of cattle in Louisiana and other states. Research Information Sheet No. 104, LSU AgCenter, 19 pp.
- Loyacano, A.F., Williams, J.C., Gurie, J., DeRosa, A.A. 2002. Effect of gastrointestinal nematode and liver fluke infections on weight gain and reproductive performance of beef heifers. Vet. Parasitol. 107:227-34.
- Sanson D.W., A.A. DeRosa, G.R. Oremus, and L.D. Foil. 2003. Effect of horn fly and internal parasite control on growth of beef heifers. Veterinary Parasitology 117: 291-300.
- DeRosa A.A, Chirgwin S.R., Fletcher J., Williams J.C., Klei T.R. 2005. Exsheathment of Ostertagia ostertagi infective larvae following exposure to bovine rumen contents from low and high roughage diets. Veterinary Parasitology (VETPAR_3091: In Press)
- DeRosa A.A., Chirgwin S.R., Williams J.C., Klei T.R. 2005. Quantitative Measurement, Isolation and Characterization of Carbonic Anhydrase from Ostertagia ostertagi Infective Larvae During In Vivo Exsheathement. Molecular and Biochemical Parasitology. (AW05002: In Review)
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Progress 01/01/03 to 12/31/03
Outputs
Genomic characterization and quantitative expression of carbonic anhydrase from Ostertagia ostertagi during the exsheathment process: Last year we isolated a small portion of a carbonic anhyrase(CA) gene from O. ostertagi. CA has not been isolated from a parasitic nematode until now. The primary hinderance is the propagation and recovery of infective larvae within the bovine host to obtain adequate amounts of genetic material from the parasites. This year we have succeeded in quantitating the expression of this enzyme during the exsheathment process and have made good progress in mapping the gene at the genomic level. To date, 2,000 bases of the promoter region have been sequenced and the first two exons and first intron of the gene representing 2,500 bases. The temporal and quantitative expression of this gene is highly correlated with the temporal pattern of exsheathment. Some insight into the regulation of this gene has already been gained from current sequencing
efforts.
Impacts
The significance of this research is to understand the biology of parasitic nematodes with the overall objective of identifiying new biological targets within these organisms for alternative control strategies. The cattle industry is currently dependent upon one drug class (macrocyclic lactones) to effectively control gastrointestinal nematodes. If widespread resistance to this drug class occurs cattle producers suffer tremendous economic losses due to decreased growth performance. The economic effects of impaired reproductive and maternal performance due to gastrointestinal parasites is difficult to assess but will also severely impact capital gains of producers. Although the life cycles and developmental patterns of gastrointestinal nematodes have been well described, virtually nothing is known about the biology of these very economically important organisms. All trichostrongylid nematodes, such as O. ostertagi, must undergo the exsheathment process before
progressing to the first parasitic stage. Parasitism is prevented if exsheathment is prevented. The goal of this research is to understand the biological pathways involved in exsheathment inorder to define new targets for anthelmintic development so that an alternative approach to controlling gastronintestinal nematodes in cattle will be available to the cattle producer.
Publications
- Sanson D.W., A.A. DeRosa, G.R. Oremus, and L.D. Foil. 2003. Effect of horn fly and internal parasite control on growth of beef heifers. Veterinary Parasitology 117: 291-300
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Progress 01/01/02 to 12/31/02
Outputs
The initial focus of this project was to 1) explore the possibility of establishing Obeliscoides cuniculi, a trichostrongylid stomach parasite of the rabbit, as a laboratory model to study the genetic basis for summer associated developmental arrest of the early fourth-stage larvae (EL4) of Ostertagia ostertagi in cattle and 2) determine if some of the commercially available goat derived antibodies that recognize dauer formation gene (daf genes) products described in the soil dwelling nematode Caenorhabditis elegans would cross react with proteins extracted from O. ostertagi . For objective 1, prior to any attempts to utilize O. cuniculi as a laboratory model, the seasonal developmental pattern of O. cuniculi in its natural host, the feral rabbit, needed to be determined. To accomplish this goal, O. cuniculi were recovered from feral rabbits harvested from various habitats in south Louisiana for 12 consecutive months. Based on the seasonal developmental pattern of O.
cuniculi observed in this survey, it was concluded that southern isolates of O. cuniculi do not undergo a summer associated developmental arrest. Consequently, O. cuniculi in rabbits would not serve as a valid model for the study of summer associated developmental arrest of O. ostertagi EL4 in cattle. This was the first description of the seasonal developmental pattern of a southern isolate of O. cuniculi from feral rabbits. A manuscript of this survey entitled, "Seasonal developmental pattern of a warm temperate isolate of Obeliscoides cuniculi in the feral rabbit", has been prepared for submission to the Journal of Parasitology. For objective 2, using western blot analysis, several attempts were made to determine the cross reactivity of goat derived antibodies against various daf gene products with protein extracts from O. ostertagi larvae. Antibodies against the dauer formation (daf) gene products of daf-2, daf-7, daf-12, and daf-16 failed to cross-react with O. ostertagi protein
extracts. Attempts to determine the genetic basis for summer associated developmental arrest of O. ostertagi in cattle have since been abandoned due to the lack of a suitable laboratory model and reagents necessary to explore this phenomenon. The current focus of this project is to isolate and describe genes expressed in O. ostertagi during the early stages of infection. We are in the process of constructing a subtracted library of genes recovered from O. ostertagi larvae after short-term exposure to the GI tract of cattle. This approach will define genes required for the transition from the free-living (non-parasitic stage) to the parasitic stage.
Impacts
Obtaining an understanding of the genetic basis of parasitism by describing the genetic pathways and mechanisms required for survival of O. ostertagi larvae in the GI tract in order to establish an infection will potentially provide new targets for the control of GI parasites in cattle. The number of effective drugs available for the control of GI nematodes is limited. Before new methods of control can be developed, an understanding of the infection process needs to be obtained.
Publications
- Loyacano, A.F., Williams, J.C., Gurie, J., DeRosa, A.A. 2002. Effect of gastrointestinal nematode and liver fluke infections on weight gain and reproductive performance of beef heifers. Vet. Parasitol. 107:227-34.
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Progress 01/01/01 to 12/31/01
Outputs
A systematic survey of worm recoveries from feral rabbits indicated that Obeliscoides cuniculi does not appear to undergo a seasonal development arrest and that the parasite is not a suitable lab model for study of warm season developmental arrest of Ostertagia ostertagi in cattle. In determination of any cross reactivity of goat-derived antibodies against Caenorhabditis elegans dauer-forming signaling proteins to O. ostertagi protein extracts by Western blot analysis, C. elegans Daf 2, Daf 16 and Daf 7 failed to produce a visible band when an O. ostertagi crude protein extract was used as antigen. It was suggested that commercially available antibodies to C. elegans signaling proteins cannot be used to measure expression of these proteins in O. ostertagi. Current focus is aimed at describing gene expression associated with the molt from free-living L3 to parasitic L4 rather than growth conditions of earlier free-living stages, L1 and L2. Calves will be surgically
fitted with abomasal cannulae to provide a portal for introducing infective O. ostertagi L3 within a digestion bag in the abomasum. Larvae will be recovered at repeated intervals from the abomasum for analysis of gene expression. The rationale for this temporal deviation from the original proposal is two-fold: 1-less time and resources needed to describe genes associated with parasitic development as possible pharmacological targets for parasite control and, 2-an excess of 5,000 expressed sequence tags from parasitic stages of O. ostertagi will be available in 2002 from the U. of Washington and USDA (Beltsville, MD) to probe eDNA libraries of parasitic L3 and L4 O. ostertagi. In a study of a long-acting injectable formulation of moxidectin (Fort Dodge), groups of (n=30/gp) crossbred beef calves were treated with saline or 1 of 3 dose levels of moxidectin (0.75, 1.0, 1.5mg/kg). At 90, 120 and 150 days after treatment, representative numbers of calves from each treatment group
(n=10/gp/date) were slaughtered for worm recovery analysis and determination of efficacy and persistence of the treatments. A high level of persistent activity was obtained at all 3 dose levels for O. ostertagi adults,inhibited and developing larvae activity also noted for adults of H. placei and T. axei. A high level of persistent activity was also found at all 3 dose levels for D. viviparus and at the highest dose only for C. punctata adults and Cooperia spp. adult females at 120 days after treatment.
Impacts
While not providing a lab. model for study of O. ostertagi larval arrest, the survey results of O. cuniculi were useful to State wildlife biologists studying annual cycles of parasitism in feral rabbits. Studies on O. ostertagi gene expression in developing stages of the parasite are ongoing and should yield results of much value in understanding larval arrest. Efficacy and field trial evaluation of new anthelmintics/formulations under Louisiana conditions are of great value for local and regional recommendations.
Publications
- Loyacano, A.F., Williams, J.C., Gurie, J. and DeRosa. 2001. Effects of subclinical infections of internal parasites on the production of beef heifers. 2001 Beef Cattle Research Report (Vol. 31), LSU AgCenter, pp. 27-29.
- Williams, J.C. 2001. Stomach and intestinal worms. Parasitology Section, Beef Cattle Production in Louisiana. A handbook, Louisiana Cooperative Extension Service, LSU AgCenter, pp. 75-79.
- Williams, J.C. and Loyacano, A.F. 2001. Internal parasites of cattle in Louisiana and other states. Research Information Sheet No. 104, LSU AgCenter, 19 pp.
- Loyacano, A.F., Skogerboe, T.L., Williams, J.C., DeRosa, A., Gurie, J. and Shostrum, V.K. 2001. Effects of parenteral administration of doramectin or a combination of ivermectin and clorsulon on control of gastrointestinal nematode and liver fluke infections and on growth performance in cattle. J. Amer. Vet. Med. Assoc. 218:1465-1468.
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