Immunity and epidemiology of helminthiasis in grazing animals

Can a combination of vaccination, probiotic and organic acid treatment in layer hens protect against early life exposure to Salmonella Typhimurium and challenge at sexual maturity?

Day old layer chicks were challenged with Salmonella Typhimurium using a seeder bird technique. Treatment groups were untreated control, administration of a probiotic in drinking water weekly, vaccination by intramuscular injection of a live aro-A deletion mutant vaccine at 10 weeks of age (woa) followed by an oral dose at 16 woa, probiotic administration plus vaccination, vaccination plus the administration of an organic acid preparation in feed from 16 woa and a combination of probiotic, vaccine and organic acid. Faecal shedding was monitored by culture at 1, 2, 3, 4, 8, 12, 15, 17, 20, 21, 23 and 25 woa and in dust from settle plates by PCR at intervals from 8 woa. Birds from each group were separated at 17 and 18 woa and challenged orally with 10⁶ CFU of S. Typhimurium. Both untreated and probiotic groups shed Salmonella until 56 days. Salmonella was also detected in dust from 8 until 12 woa but little after this. After vaccination, from sexual maturity (18 woa) all groups except those that were vaccinated with and without probiotic re-excreted Salmonella. The probiotic alone was ineffective against this re-excretion and all groups receiving organic acids shed Salmonella. At 17 woa, unchallenged controls were fully susceptible to caecal colonization, however all other groups showed reduced susceptibility, including the untreated challenged group. However, at 18 woa (sexual maturity) only the groups that were vaccinated with or without probiotic showed reduced susceptibility to colonization. The organic acid treated groups (including the vaccinated group) did not show a difference to the untreated controls. S. Typhimurium demonstrated an ability to re-emerge at sexual maturity, similar to other serovars. The vaccine assisted in limiting the re-excretion at sexual maturity and decreased susceptibility to subsequent challenge. Use of a probiotic augmented the vaccine's protective capacity.

Interaction of parasitism and nutrition and their effects on production and clinical parameters in goats

Weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial design experiment for 5 months to test the main effects and interaction of two levels of nutrition (growth + maintenance, NUT1; twice growth + maintenance, NUT2) and three levels of Haemonchus contortus burden (0, 500 and 2000 larvae administered every 2 weeks: W0, W500 W2000, respectively) on weight, feed intake, level of infection and packed cell volume (PCV). The rationale for the experimental design was based on the lack of information concerning the interaction between nutritional status and worm burden. Results indicated significant effects of worm burden levels on PCV, faecal egg contents (eggs per gram of feces (EPG)), actual worm numbers, feed intake and efficiency of feed utilization. Nutrition x worm burden interactions were also significant for PCV and EPG. However, the differences detected for PCV and actual worm numbers did not translate into large or consistent differences in body weight. Goats on NUT2, after an initial period, showed little difference in body weight, irrespective of worm burden. Within the NUT1 level, W0 kids weighed more than W500 or W2000 kids throughout the study. Although not statistically significant, this constitutes a trend towards an interaction between nutrition and worm burden. In both nutrition levels, there were no body weight differences between W500 and W2000 until the last 14 days. Feed intake was depressed in the first 3 months of the experiment for infected animals, but was subsequently followed by a compensatory reaction. Lower establishment rates, based on actual worm counts, were observed for the higher infection level, but in both infection levels establishment rates tended to decrease with time. Nutrition was found to be more important to counteract the consequences of a parasitic infection than to counteract the establishment of that same infection.

Haemonchosis in sheep and goats in Sierra Leone

The incidence of haemonchosis in sheep and goats in Sierra Leone showed a seasonal variation with a high peak in the dry season (October to January) and a low one from March to May. Mean relative densities were significantly higher in young hosts and showed two peaks, a high one from August to December and a low one from April to June while the mean relative densities of old hosts were low and exhibited an irregular seasonal pattern with no defined peaks. The peak seasons in young hosts coincided approximately with the dry and rainy seasons. Male hosts showed an overall higher but not a significant mean relative density than females but for most of the months mean relative densities of infection of female hosts were not significantly higher than those of males. The roles of climatic conditions and arrested development (hypobiosis) and self-cure and host age immunity on Haemonchus contortus worm burdens are discussed.

Inhibition phenomena mechanisms in experimental obeliscoidosis in rabbits. II. Local and systemic antibody responses

A series of experiments was carried out using adult outbred Polish race rabbits of both sexes infected, during spring or autumn, with 10,000 larvae of Obeliscoides cuniculi, either fresh or stored at 4 degrees C. Extracts of mucosal proteins and bile were collected at postmortem 6 or 12 weeks after infection. Antibody levels were determined in antisera, bile and stomach mucosa by haemagglutination and precipitation tests. Local antibody responses were demonstrated in the stomach and bile, and reactions were obtained with the tissue fluids by haemagglutination and precipitation tests with worm antigens and ES products. Additionally, some specific immunological response was observed in the circulation during the primary infection. These results suggest a clear-cut relationship between increased levels of these antibodies and either larval inhibition or worm expulsion during O. cuniculi infections.

Effect of anthelmintic treatment immediately after calving on milk production

The effects of anthelmintic treatment on the milk production of cows subjected to contrasting nutritional conditions before and after calving were determined. Half of the cows in each of 2 management treatments were treated with 3.75 grams of fenbendazole on the second day after calving and twice more at weekly intervals. Treated and control cows were grazed together for the entire lactation. Treated cows produced 8% more (P less than 0.05) milk over the 20 weeks lactation than the untreated cows. One third of the total lactation response to anthelmintic treatment occurred during weeks 5 to 10 of lactation. The observed responses occurred despite equal larval challenge to treated and control cows and therefore the responses obtained are discussed in the context of a reduction in the worm burden.

Helminth parasites of beef cattle in the East Kimberley and Victoria River Districts of Northern Australia

An investigation into the helminth species present in cattle in the East Kimberley and Victoria River Districts of Northern Australia was conducted over a 2-year period based on bi-monthly total and differential worm counts in weaner cattle as well as on a post mortem survey of adult cattle sent for slaughter. The most important species found in young cattle were Haemonchus placei and Cooperia spp. Only small numbers of Bunostomum phlebotomum, Nematodirus spathiger, Oesophagostomum radiatum and Moniezia benedini were present. Calicophoron calicophorum and nodules of Onchocerca spp. and Oe. radiatum were recorded in adult cattle. Seasonal fluctuations in helminth parasite burdens are discussed in relation to temperature and rainfall and the results are interpreted in relation to the effects of helminthosis on present and future beef production in this area.