Immunity of calves treated with an oxfendazole pulse release bolus to challenge with Dictyocaulus viviparus

Immunomodulatory effect of various anti-parasitics: a review

This paper reviews the immunomodulatory effects (immunosuppression or immunoactivation) of various anthelmintics including levamisole, fenvalerate, dieldrin, carbofuran, aminocarb, thiabendazole, fenbendazole, oxfendazole and ivermectin. The induced modulation of immune function may occur via direct and/or indirect mechanisms. The immunomodulatory effects of these anti-parasitics have been studied in a variety of bacterial (e.g. brucellosis, salmonellosis, paratuberculosis, mastitis), viral (e.g. infectious bovine rhinotracheitis, Herpes, foot and mouth disease), parasitic (e.g. onchocerciasis, coccidiosis, ascariasis, schistosomiasis) and neoplastic diseases. Some antiparasitics have also been used to boost immunity in a number of human diseases including leprosy, Hodgkin's disease, rheumatoid arthritis, and in adjuvanted therapy of colorectal cancer. The ability to stimulate the immune response of animals offers a new means of disease intervention. Future research on immunomodulatory effects of anti-parasitics, for humans and domestic farm animals, will provide additional methods of treating immunosuppressed subjects. The immunopotentiating or immunosuppressing activity of anti-parasitics will dictate whether co-administration of vaccines and anthelmintics or administration of vaccines during the window of immunoactivation is justified or not.

Prophylaxis of bovine trichostrongylidosis and dictyocaulosis in the alpine region: comparison of an early and late administration of the oxfendazole pulse release bolus to first year grazing calves

The effect of the oxfendazole pulse release bolus (OPRB) administered at turnout, in May, or in mid-July on the development of infections with gastrointestinal nematodes and lungworms in first year grazing calves was investigated with three groups of nine animals, all grazing the same pastures in the Swiss midland region. In the calves of Group A (OPRB on 21 May) less than 20 eggs per gram of faeces (e.p.g.) and less than three Dictyocaulus larvae per 10 g (1.p.10 g) of faeces were shed for a period of 126 and 140 days respectively. Towards the end of the grazing period calves of this group excreted significantly higher levels of lungworm larvae (P < 0.05) compared with the other groups. Prior to OPRB administration on 14 July, the calves of Group B developed subclinical infections with trichostrongyles and lungworms which were similar to the untreated control Group C. By 4 weeks after bolus-administration the excretion of trichostrongylid eggs and lungworm larvae declined to levels below 20 e.p.g. and six l.p.10 g respectively. Serum pepsinogen values of the calves of Groups A and B were significantly lower (P < 0.05) compared with the control animals on days 84 and 98 after turnout and reflected mainly subclinical infections. With the exception of one Group A calf developing clinical parasitic gastroenteritis (p.g.e.) at the end of the season, clinical disease was not observed in the treated calves, while seven out of nine control animals grazing on the same pastures exhibited clinical p.g.e. with mean serum pepsinogen values exceeding 4400 mU tyrosine. Calves of Groups A and B gained significantly more weight (P < 0.01) compared with Group C (+36 kg and +41 kg respectively); differences between Groups A and B were not significant. The results indicate that in mixed grazing systems of treated and untreated calves, which are often found in the alpine region, administration of the OPRB in May or July provided good results with respect to performance of the calves. However, late administration of the OPRB has the additional advantage of coverage of the period of higher infection risk with trichostrongyles and lungworms in the late season until stabling, and should therefore be recommended.

The development of protective immunity against gastrointestinal nematode and lungworm infections after use of an ivermectin bolus in first-year grazing calves

Interactions between treatment with an ivermectin bolus at turnout and immunity to bovine parasitic gastroenteritis and bronchitis were examined. Immunity related parameters, i.e. development of clinical disease, parasite development and stimulation of parasite specific antibodies were examined for two grazing seasons and compared with untreated second season cattle (immune control) and untreated parasite naive cattle (nonimmune control). With respect to gastrointestinal nematodes, clinical condition, body weight development, faecal egg counts and pepsinogen concentrations of the bolus treated animals were not significantly different from the respective values of untreated immune cattle, showing a considerable degree of resistance in both groups compared to the parasite naive cattle. With respect to lungworms, untreated immune cattle were protected against clinical disease, but two of eight animals shed larvae again. Bolus treated animals transiently showed mild clinical symptoms and six of seven animals shed low numbers of larvae again, whereas all parasite naive cattle shed high numbers of lungworm larvae and showed signs of disease during the whole grazing season. In spite of the effective treatment with an ivermectin bolus during the first year a considerable resistance to gastrointestinal nematode and lungworm infection was present in the second grazing season.

Response of cattle treated with a fenbendazole slow release bolus to challenge from nematodes the following season

Nematode infection of cattle treated in their first year at pasture with the fenbendazole slow release bolus ('Bolus group') was compared during the second year with that of untreated cattle. Ostertagia was the most prevalent parasite associated with Cooperia. Except for the Dictyocaulus spp. which caused clinical signs of bronchitis in the 'Bolus' group, the infection during the second year resulted in a moderate response of the cattle whatever the group. Rises in both pepsinogen and gastrin levels were correlated with the number of Ostertagia L3 on herbage. Damages in the abomasal mucosa were more frequent and severe in the 'Bolus' group where more inflammatory signs were observed in spite of a smaller number of worms. Nevertheless, the differences in total weight gains were not significant thanks to a compensatory effect during the second part of the grazing season in the 'Bolus' group. Hypotheses related to a minimum threshold of infection during the first year necessary to develop high enough protection during the second year are discussed. The pathological effects of gastrointestinal nematodes seem to vary more according to the inflammatory response than to the number of worms.

Efficacy of Michel's 'dose and move' system against Dictyocaulus viviparus infections in cattle using moxidectin as anthelmintic

Two grazing experiments were performed to study the effect of moxidectin in a 'dose and move' system on Dictyocaulus viviparus infections in calves. In the first experiment, three groups of four calves were experimentally infected with 20 larvae of D. viviparus 7 weeks before moxidectin treatment of two of these groups. A sufficient suppression of Dictyocaulus infections was observed in a 'dose and move' group, but also in a group which stayed on contaminated pasture after treatment. In contrast, high faecal larval counts and lungworm disease were observed in July-August in a non-treated pasture control group. Development of immunity against lungworm was sufficient in all three groups, on pasture. In the second experiment, four out of 26 calves, including two groups of six calves and four tracer calves, were experimentally infected with 20 larvae of D. viviparus 7 weeks before moxidectin treatment combined with a move of one of the groups. No lungworm disease was observed in this 'dose and move' group. In a pasture control group high faecal larval counts and severe clinical disease were observed in August-September and one calf had to be euthanized. Although a mean burden of 129 immature lungworms was present at the time of treatment, development of immunity appeared to be low in the 'dose and move group'. In contrast, high levels of immunity had developed in the pasture control group.

An experimental field study on the build up of lungworm infections in cattle

The build up of lungworm infections was studied in four groups of calves. Calves of Group 1 were infected experimentally with 6 x 10 larvae during the first 3 weeks after turnout. The pasture of Group 2 was contaminated with approximately 35,000 larvae in June and the pasture of Group 3 with approximately 1.3 million larvae in August. Group 4 served as the helminth free control group for challenge infections with 5,000 larvae in October. In Group 1 faecal larval counts increased 5 weeks after the beginning of patency and decreased after another 3 weeks, indicating the development of immunity after the second lungworm generation. In contrast, the development of immunity in Groups 2 and 3 occurred after the first lungworm generation as maximal faecal larval counts were seen within 3.5 weeks after the beginning of patency. Infection levels were highest in Group 3 which was the only group showing clinical signs. These signs became worse after oxfendazole treatment.

Oxfendazole treatment of non-parasitized lambs and its effect on the immune system

Ten parasite-free lambs were drenched with oxfendazole on days 0 and 28 and, one day after each drench, were injected with human erythrocytes and ovalbumin. Ten other antigen-injected lambs were not drenched (controls). Lymphocytes collected 3 days after each antigen injection and cultured in RPMI 1640 plus 5% fetal calf serum (FCS) and lymphocytes collected 3 days after the first and 3 and 7 days after the second antigen injection and cultured in 50% autologous serum had decreased blastogenic activity compared with control lymphocytes. After the second drench, decreased blastogenesis was seen with lymphocytes collected on days 3 and 7 and cultured in 5% FCS and concanavalin A (Con A) and on day 3 when cultured in 5% FCS and phytohaemagglutinin (PHA). Decreased blastogenesis was also seen with lymphocytes collected 7 and 29 days after the second injection of antigen and cultured in 50% autologous serum plus Con A and on days 3, 7 and 29 when cultured in 50% autologous serum and PHA. Significantly depressed antibody responses to both antigens were seen after the second drench. The serum complement level was depressed 3 days after the second injection of antigen. Serum nitric oxide levels were significantly depressed 3 and 21 days after the first and 7 and 21 days after the second injection of antigen. There were no differences in levels of growth-promoting hormones but the drenched lambs gained significantly more weight than the controls.

Effect of sustained release and pulse release anthelmintic intraruminal devices on development of pathophysiological changes and parasite populations in calves infected with Ostertagia ostertagi and Cooperia oncophora

An experiment was conducted in calves to investigate the effect of sustained release and pulse release anthelmintic intraruminal boli on the development of pathophysiological changes following daily infection with Ostertagia ostertagi and Cooperia oncophora for six weeks. After infection various pathophysiological changes were detected including increases in serum pepsinogen concentration, enteric plasma protein losses and in the catabolic rate of albumin. Such changes developed rapidly in the unprotected calves following patency after 17 days and persisted until the termination of the study. There were indications that the sustained anthelmintic release device was more efficacious than the pulse anthelmintic release device in reducing the worm burdens and early pathophysiological changes associated with infection. It was found at necropsy that the release of anthelmintic by the oxfendazole pulse release bolus had been delayed in several calves.