Gastrointestinal Parasite Burden Research Articles

Identificação de Cooperia punctata (Linstow, 1907) resistente a ivermectina e doramectina em um rebanho leiteiro no Estado do Rio de Janeiro, Brasil

Resistência antihelmíntica é um problema potencial para o controle de nematodas em bovinos e pode causar perdas econômicas na indústria de bovinos leiteiros e de cortes. O objetivo deste estudo foi determinar a eficácia da ivermectina, doramectna e abamectina em bezerros infectados naturalmente e experimentalmente para Cooperia punctata em um rebanho bovino leiteiro. Testes de redução da contagem de ovos fecais foram conduzidos em bezerros infectados naturalmente que foram tratados com soluções injetáveis de ivermectina, doramectina e abamectina. Amostras fecais foram colhidas no dia do tratamento, dia 0, e nos dias 7 e 14 após o tratamento e cultura de larvas foram feitas nas amostras positivas. Um teste controlado foi realizado usando 18 bezerros infectados artificialmente,alocados em três grupos com seis animais cada: Grupo I - controle, sem tratamento; Grupo II - ivermectina, solução injetável, 200µg/kg; Grupo III - doramectina, solução injetável, 200µg/kg. Amostras fecais foram colhidas no dia do tratamento, dia 0, e nos dias 3, 7, 9 e 14 após o tratamento. Nos dias 14, 15 e 16, dois animais de cada grupo foram eutanaziados e cargas de parasitos pulmonares e gastrintestinais foram determinados. Os resultados dos testes de redução da contagem de ovos fecais em bezerros infectados naturalmente mostraram redução no dia 14 após o tratamento de - 4,45 a 11,49% para ivermectina; 32.31 a 60.40% para doramectina e 85,05% para abamectina. O único parasito identificado na cultura de larvas foi Cooperia spp. O Teste Controlado mostrou uma redução da contagem de ovos fecais no dia 14 após o tratamento de 51.47% e 96.08% para ivermectina e doramectina, respectivamente. Redução da contagem de adultos neste teste controlado foi de 53.91% e 82.43% para ivermectina e doramectina, respectivamente. Somente C. punctata foi recuperado nas necropsias. Assim, esta cepa de C. punctata foi considerado resistente ao tratamento com ivermectina e doramectina e sugere uma possível resistência para abamectina pelo teste de redução da contagem de ovos fecais.

A longitudinal study of gastrointestinal parasites in Canadian dairy farms: The value of an indirect Ostertagia ostertagi ELISA as a monitoring tool

The general objective of this study was to evaluate a crude Ostertagia ostertagi antigen enzyme-linked immunosorbent assay (ELISA) for monitoring gastrointestinal parasites in lactating dairy cattle. A longitudinal study of gastrointestinal parasites in lactating dairy cows was carried out in 38 herds in four provinces of Canada (Prince Edward Island, Quebec, Ontario and Saskatchewan) from September 1999 to October 2000. Bulk tank milk, cow milk, serum and fecal samples were collected monthly or quarterly from all these farms. Information on herd management factors was collected by a standard questionnaire and individual cow production data were obtained from an electronic database. The overall mean optical density ratio (ODR) was 0.30 and ranged from −0.05 to 1.55. Although a clear seasonal pattern was not observed, the ODR values tended to decrease during the housing period and start increasing in the spring before the cows went out to pasture. The second and third or greater lactation cows had significantly higher ODR values compared with first lactation animals. The individual cow ODR had a very low correlation with individual squared root fecal egg counts but showed a reasonably high correlation when herd averages values were computed ( r=0.73). A moderate correlation ( r≈0.50) between the bulk tank and herd average ODR was observed. Milk yield was negatively associated with individual cow milk ODR and a quadratic effect on ODR was observed for days in milk. Twenty-eight of the herds participated in a clinical trial of eprinomectin (Ivomec ® Eprinex ®) treatment at calving. The cow level ODR values determined late in the previous lactation had a marginally significant effect ( P=0.07) on treatment response, suggesting that high OD cows responded better to the anthelmintic treatment. However, because of the small sample size available in this model, more research is needed to better understand this relationship. In conclusion, the indirect ELISA using an O. ostertagi crude antigen appears useful as a technique for monitoring gastrointestinal parasite burdens in adult dairy cows and holds promise as a potential predictor of response to anthelmintic treatment.

Altered immune responses to a heterologous protein in ponies with heavy gastrointestinal parasite burdens.

This study was performed to test the hypothesis that immunity to heterologous vaccination would improve when the parasites were removed. It was also expected that parasitised ponies would exhibit a biased Th2 cytokine response to KLH immunisation. Helminth parasites are common in horses even in the era of highly effective broad-spectrum antiparasiticides. These parasites have been shown to alter the outcome to heterologous immunisation in a number of host species. The effect of gastrointestinal parasites on heterologous vaccination has not been addressed in equids. In the current study, humoral, lymphoproliferative, and cytokine responses to a single i.m. injection of keyhole limpet haemocyanin (KLH) were compared between groups of ponies with high, medium or low gastrointestinal parasite burdens. Antibody levels determined by ELISA showed that animals with low levels of parasites had a trend toward increased KLH specific total immunoglobulin, IgG(T) and IgA compared to heavily parasitised ponies. Medium and heavily parasitised ponies demonstrated a trend toward reduced lymphoproliferative response to KLH that was not restored after the addition of interleukin-2 (Il-2). Cells from these ponies also produced significantly lower levels of IL-4 compared to lightly parasitised ponies. These data indicate that heavily parasitised ponies have uniformly decreased cellular and humoral immune responses to soluble protein immunisation. The mechanisms involved may have potential deleterious effects on standard vaccine protocols of parasitised equines.

PARASITE-MEDIATED SELECTION AGAINST INBRED SOAY SHEEP IN A FREE-LIVING ISLAND POPULATON.

Parasites are thought to provide a selective force capable of promoting genetic variation in natural populations. One rarely considered pathway for this action is via parasite-mediated selection against inbreeding. If parasites impose a fitness cost on their host and the offspring of close relatives have greater susceptibility to parasites due to the increased homozygosity that results from inbreeding, then parasite-mediated mortality may select against inbred individuals. This hypothesis has not yet been tested within a natural vertebrate population. Here we show that relatively inbred Soay sheep (Ovis aries), as assessed by microsatellite heterozygosity, are more susceptible to parasitism by gastrointestinal nematodes, with interactions indicating greatest susceptibility among adult sheep at high population density. During periods of high overwinter mortality on the island of Hirta, St. Kilda, Scotland, highly parasitised individuals were less likely to survive. More inbred individuals were also less likely to survive, which is due to their increased susceptibility to parasitism, because survival was random with respect to inbreeding among sheep that were experimentally cleared of their gastrointestinal parasite burden by anthelminthic treatment. As a consequence of this selection, average microsatellite heterozygosity increases with age in St. Kildan Soay sheep. We suggest that parasite-mediated selection acts to maintain genetic variation in this small island population by removing less heterozygous individuals.

Selection for Foraging Efficiency During a Population Crash in Soay Sheep

1. There are surprisingly few examples of the fitness consequences of variation in foraging traits, despite their importance for survival and reproduction. We studied the relationship between traits affecting foraging efficiency and individual fitness in Soay sheep on the island of St Kilda, Scotland. 2. Survival during an over-winter population die-off was related to variation in incisor arcade breadth, a morphometric trait that is known to influence food intake. Other morphometric measures, such as body dimensions and weight, were less well related to survival. 3. Individual survival over winter was also related to gastrointestinal parasite burden, estimated in faecal samples in the previous August. Incisor arcade breadth and parasite burden affect nutrient assimilation rate, energy balance and susceptibility to mortality through starvation. An energetic model developed to predict energy intake and expenditure from incisor arcade structure, body reserves and thermal balance was no better at predicting individual survival than incisor breadth alone. 4. Our results raise questions about stabilizing selection on incisor breadth and the effect of spatial heterogeneity in the vegetation on selection pressure in different home ranges. We discuss the way pleiotropic effects may operate through increased fitness of animals with narrow incisor arcades feeding more selectively when food is plentiful at low population density.

Effects of feed plots on fecal egg counts of white-tailed deer

Effects of feed plots on concentrations of gastrointestinal nematode eggs (eggs per g; EPG) in feces of white-tailed deer ( Odocoileus virginianus) were studied on six properties in East Feliciana Parish, LA, USA, from February 1989–January 1990. EPG levels were weakly related to deer densities ( r=0.11, P < 0.01) and differed among seasons ( P = 0.02), months ( P < 0.01), and properties ( P < 0.01). EPG levels from samples collected monthly on individual properties averaged 14.8 (SE =1.3). EPG levels during winter and summer were similar ( P > 0.05) and higher than during fall or spring. EPG levels during spring were lower than during any other season ( P < 0.05). The presence of feed plots did not affect EPG levels during any season ( P >- 0.34) or month ( P >- 0.18), or with relative deer density serving as a covariable ( P=0.52). The presence of feed plots did not affect gastrointestinal parasite burdens of deer as reflected by fecal egg counts on properties in this study. The establishment of feed plots will not necessarily lead to increased gastrointestinal parasite burdens in deer concentrating to forage on those sites.

Dynamics of Ostertagia spp. and Cooperia oncophora in field-grazed cattle from weaning to 2 years old in New Zealand, with particular reference to arrested development.

Gastrointestinal nematode parasite burdens were monitored in a herd of field-grazed cattle from weaning to 2 years old to allow observations to be made on the dynamics of burdens of arrested Ostertagia spp. and Cooperia oncophora. Arrested Ostertagia spp. accumulated in the herd over their first autumn and winter to reach a peak in late winter/spring (August-October). From October until late January they declined at a rate comparable to that at which they had accumulated. Numbers continued to decline at a slower rate until the following autumn (May) when they began to increase again. Observations on the decline of worm burdens in a group of animals which had been moved from pasture to worm-free conditions in October indicated that intake of infective larvae over late spring/summer contributed little to the number of arrested Ostertagia spp. in the herd. No clinical Type II ostertagiosis was observed in the field-grazed animals over the time of decline of the arrested worm burden, nor was there an increase in the number of adult Ostertagia spp. present. However, two of the animals removed from pasture to worm-free conditions developed Type II ostertagiosis approximately a month after the move. Worm burdens of successive groups of "tracers" grazed with the herd every 2 months indicated that there was a small seasonal increase in the propensity of Ostertagia spp. for arrested development. However, estimated accumulation rates of arrested larvae calculated from tracer worm burdens, suggest that this seasonal increase in propensity was not adequate in itself to account for the accumulation rate observed in "resident" animals of the herd. No comparable accumulation of arrested C. oncophora took place in resident animals over the first autumn and winter of the trial despite the fact that tracer worm burdens over this period indicated a marked seasonal increase in the propensity for arrested development by this species.

Efficacy of Morantel Tartrate in a Sustained Release Bolus on the Control of Subclinical Gastrointestinal Parasitism in First-Year Grazing Dairy Replacements

Thirty-four heifers (24 Holstein, 8 Ayrshire, 2 Jersey) and 12 Holstein steer calves were grouped into 23 blocks of 2 animals each according to breed, sex, and body weight. Animals in each block were randomly assigned to control or treated groups. The treated group received an anthelmintic bolus containing morantel tartrate before they were permitted access to pasture. A 2.6ha pasture was divided in half with a double fence; the resulting two pastures had separate feed and water troughs. Steer calves were slaughtered upon termination of the trial to ascertain gastrointestinal parasite burdens. Two worm-free tracer calves were placed on each pasture every 2 mo and slaughtered after 4 wk of grazing to determine parasite infectivity of pastures. Herbage samples were obtained monthly and analyzed for infective larvae. The trial was conducted for 141 d during the grazing season. Treatment resulted in 90% reduction in infective larvae on pasture, 74% reduction in fecal worm-eggs, 91% reduction in adult worm burdens, and a trend toward reduced worm burdens in tracer calves by 52%. An overall average daily gain of .68 and .88kg was obtained for control and treated animals. Reproductive data for the heifers remaining in the herd from the trial showed that treatment resulted in 44 less days to first breeding.