Inhibited development of Ostertagia spp. and Cooperia spp. in naturally acquired infections in calves

Abstract

Aujeszky? disease is predominantly a nervous disease of piglets, weaners, and fatteners in which the mortality may vary from 540%. Respiratory disease is also a feature of infection with certain strains of the virus. Infection of pregnant sows may cause abortion, stillbirths, and mummification, and infertility may result in both boars and sows. Traditionally the serum neutralisation test has been used as an indicator of past infection with Aujeszky s's disease virus (ADV). However, cell-mediated immunity has recently been shown to play an important role in recovery and protection from infection with ADV and antibody-dependent cell-mediated cytotoxicity can be used as an alternative diagnostic test for detection of antibody. A number of inactivated, and live, avirulent vaccines are now available for control of the disease but their use is contraindicated in countries such as New Zealand which have a low prevalence of infection. Where possible early eradication is the best policy to follow.     

Observations on the resumption of development of inhibited Ostertagia, Cooperia and Nematodirus infections in calves stabled overwinter.

Two groups of three month old, parasite-free calves grazed a permanently infected pasture for 14 days, Group A during the first two weeks of September and Group B during early November. Half of each group was killed 14 days after removal from the pasture and the remainder stabled overwinter before slaughter and parasitological examination. Marked inhibition of development occurred for Cooperia oncophora with a variable lower level of inhibition for Ostertagia ostertagi and practically none for Nematodirus helvetianus in those calves grazing late in the fall. Under the conditions of this study, inhibited Cooperia larvae resumed development in several calves soon after they were stabled while small numbers of Ostertagia resumed development regularly during the winter and spring with a considerable number of Ostertagia still present when the calves were slaughtered at the end of the stabling period. On the other hand, Nematodirus and practically all Cooperia worms were lost during the stabling period. In three of seven calves grazing late fall pastures, large Cooperia infections were either not established or failed to become patent.     

Dermal responses to Ostertagia ostertagi in Ostertagia ostertagi- and Cooperia punctata-inoculated calves

Calves harboring patent Ostertagia ostertagi or Cooperia punctata were given intradermal injections of O ostertagi 3rd-stage larval antigen. The initial injections were followed 30 days later by a 2nd series of injections. Skin thickness was measured at injection sites for 72 hours after injection. Selected injection sites including saline solution control sites were biopsied at 30 minutes, at 3, 24, 48, and 72 hours, and at 30 days after injection. After the 1st series of injections, there was a clear distinction in dermal reactions between O ostertagi-inoculated calves and C punctata-inoculated calves; after 24 hours, reactions were not seen in the C punctata-inoculated calves. Marked dermal reactions occurred in the O ostertagi-inoculated calves. The reactions at 30 minutes and 3 hours were characterized by slight-to-extensive infiltration of neutrophils and dermal edema. The 24-hour cellular reaction was principally due to neutrophil and eosinophil infiltration with edema and necrosis. Reactions at 48 to 72 hours were due to eosinophils and perivascular accumulations of macrophages and lymphocytes. Necrosis, neutrophils, and edema were present in foci where fragments of nematodes were located. On reinjection, a clear distinction in dermal reactions between calves was not seen based on the type of nematode infection. Thirty days after dermal inoculation, large nodules developed at the site of the initial antigen injection. The nodules were characterized by marked intradermal proliferation of lymphocytes in a follicular pattern with occasional macrophages and rare multinucleated giant cells.     

Age resistance in calves to Ostertagia ostertagi and Cooperia oncophora

Calves were infected repeatedly during a period of 6 weeks with Ostertagia ostertagi and Cooperia oncophora, at an age of 3, 6 or 9 months. The inoculations were performed during three periods, February-March, May-June and August-September, to account for possible seasonal effects or effects of larval batches. Observations were done on faecal egg output, antibody titres and weight gains. Calves were slaughtered for post mortem examinations 9 weeks after the start of infections. The influence of age on worm populations and egg output was significant for C. oncophora but not for O. ostertagi. The effect of season or larval batch on worm populations was significant for O. ostertagi but not for C. oncophora. The correlations between worm numbers and several other parameters found for Cooperia were strongly indicative of a process of worm expulsion taking place at the stage of infection (9 weeks after the start of infections) when post mortem examinations were done. Such correlations were absent for Ostertagia. It is concluded that within the range of ages examined here (the range to which first season grazing calves belong), there is no influence of age on Ostertagia populations but a clear effect of age on Cooperia. This difference strongly influences the total faecal egg output of grazing calves and its interpretation.     

Negative interactions between Ostertagia ostertagi and Cooperia oncophora in calves

The interactions between Ostertagia ostertagi and Cooperia oncophora were studied in calves by concurrent and sequential infections. A reciprocal negative interaction between the 2 species was found in sequential, but not in concurrent infections. This result was supported by the finding of serological cross-reactions. It is suggested that the negative interaction is immunologically mediated. The depression of weight gain found after infection was similar for O. ostertagi- and C. oncophora-infected calves.     

Resistance to moxidectin and abamectin in naturally acquired Ostertagia circumcincta infections in sheep

AIM: To investigate the occurrence of resistance to macrocyclic lactone (ML) anthelmintics by Ostertagia circumcincta in lambs on a sheep and cattle property in the North Island of New Zealand. METHODS: Thirty lambs were randomly allocated to one of five equal-sized groups, consisting of an untreated control and four treatment groups. The treatments, which were administered at the manufacturer's recommended dose rates, included oral moxidectin, oral abamectin (both at 0.2 mg/kg), an albendazole-levamisole combination, and an albendazole-levamisole-ivermectin combination. Post mortem worm counts were undertaken 7 days after treatment to determine the efficacy of each anthelmintic. RESULTS: The albendazole-levamisole and albendazole-levamisole-ivermectin combinations both reduced O. circumcincta burdens to zero whereas for moxidectin and abamectin efficacies of only 72% and 29%, respectively, were recorded. CONCLUSIONS: These results clearly demonstrated the occurrence of resistance to MLs by O. circumcincta. Although this is not the first occasion where resistance to this anthelmintic family has been detected in this parasite in sheep in New Zealand, it is the first instance that resistance to either moxidectin or abamectin has been reported.     

Resistance to moxidectin and abamectin in naturally acquired Ostertagia circumcincta infections in sheep

AIM: To investigate the occurrence of resistance to macrocylic lactone (ML) anthelmintics by Ostertagia circumcincta in lambs on a sheep and cattle property in the North Island of New Zea- land.

METHODS: Thirty lambs were randomly allocated to one of five equal-sized groups, consisting of an untreated control and four treatment groups. The treatments, which were administered at the manufacturer's recommended dose rates, included oral moxidectin, oral abamectin (both at 0.2 mg/kg), an albendazole-levamisole combination, and an albendazole-levamisole-ivermectin combination. Post mortem worm counts were undertaken 7 days after treatment to determine the efficacy of each anthelmintic.

RESULTS: The albendazole-levamisole and albendazole-levam-isole-ivermectin combinations both reduced O. circumcincta burdens to zero whereas for moxidectin and abamectin efficacies of only 72% and 29%, respectively, were recorded.

CONCLUSIONS: These results clearly demonstrated the occurrence of resistance to MLs by O. circumcincta. Although this is not the first occasion where resistance to this anthelmintic family has been detected in this parasite in sheep in New Zealand, it is the first instance that resistance to either moxidectin or abamectin has been reported.     

Arrested development of bovine Ostertagia spp. and Cooperia spp. in New Zealand. Effect of temperature and duration of storage on infective larvae

Infective larvae of Ostertagia spp. and Cooperia spp. derived from naturally infected dairy calves were subjected to periods of storage of up to 16 weeks at 4 degrees C or 15 degrees C to determine if this treatment would influence their propensity for arrested development in previously worm-free calves. Results showed no significant increase in the propensity of Ostertagia spp. for arrested development in response to the treatments, but a small increase in the case of Cooperia spp.     

Establishment and pathogenicity of two strains of Ostertagia ostertagi and Cooperia oncophora in calves in different locations.

An experiment was carried out simultaneously in Glasgow and in Wageningen to investigate possible differences between the local strains of Ostertagia ostertagi and Cooperia oncophora. In each location calves of the local Friesian breed were infected with 100,000 larvae of either the Glasgow or Wageningen strain of O ostertagi or C oncophora. At both locations the calves received the same diet. The Glasgow strain of O ostertagi was more pathogenic than the Wageningen strain and a larger proportion of the worm burden was found in the abomasal mucosa. The number of ova per female was greater in the Wageningen strain. For C oncophora the Wageningen strain gave rise to higher worm burdens and longer worms. Differences were also present between locations. The British Friesians had higher worm burdens of C oncophora and the worms of this species were longer in this host. Compared with the Dutch Friesians the British calves had a higher proportion of O ostertagi in the mucosa. This experiment showed how difficult it is to compare data from the literature because of differences in parasite and host strains and laboratory techniques.     

The efficiency of levamisole, thiabendazole and fenbendazole against naturally acquired infections of Ostertagia ostertagi in cattle

In two experiments, conducted in cattle with naturally acquired infections of Ostertagia ostertagi, comparative assessments were made of the anthelmintic efficiency of levamisole, thiabendazole and fenbendazole, each at 1.0, 1.5 and 2.0 times the recommended dose rate. Variable efficiencies of 81 and 49 per cent for levamisole, 86 and 56 per cent for thiabendazole were obtained against adult O ostertagi. Neither drug showed substantial activity against early fourth stage larvae. Efficiency of fenbendazole against adult O ostertagi was consistently high; 85 and 89 per cent in the two experiments respectively. In the first experiment in which cattle were slaughtered two to three days after treatment, only 22 per cent of inhibited early fourth stage larvae were removed whereas in the second experiment when slaughter took place 10--11 days after treatment, this efficiency was 89 per cent. There was no increased effect of increased dose rates on treatments with thiabendazole or fenbendazole. The activity of levamisole against adult worms and inhibited larvae was increased at twice the recommended dose rate.     

Pathophysiological and parasitological studies on Cooperia oncophora infections in calves

Calves which had received daily infections of Cooperia oncophora over a six week period showed inappetence, weight loss, impaired nitrogen retention and a loss of plasma proteins into the gut. During this period the infections occurred in the duodenum, jejunum and ileum and many larval stages were present in the mucosa of the small intestine. At necropsy, on weeks 3, 6 and 10 after the first infection, stunting and thickening of the villi were noted with excessive mucus production. Prior administration of a morantel slow release bolus prevented these changes. By week 12 most of the worms had been expelled yet a loss of plasma proteins to the gut was still occurring.     

Pathophysiological and parasitological studies on Ostertagia ostertagi infections in calves

Friesian calves given a low level infection of the abomasal parasite Ostertagia ostertagi over a six week period displayed a mild diarrhoea with high faecal egg counts and elevated plasma pepsinogen values. At necropsy on day 23 abomasal lesions characteristic of ostertagiasis were widespread. At 42 and 84 days oedema and congestion were also prominent. Total worm burdens on days 23 and 42 were similar but a marked decrease had occurred by day 84. Feed digestibility and nitrogen economy were not markedly affected but radioisotopic measurements demonstrated an increase in albumin disappearance and catabolic rates, and plasma faecal clearance during the course of the infection. Prior administration of a morantel sustained release bolus to a group of similarly infected calves reduced the total worm burdens to less than 50 per cent of those recorded in the infected calves on days 23 and 42 and this fell to 3 per cent on day 84. Abomasal damage and the adverse pathophysiological changes associated with infection were prevented in this group.     

Increased establishment of lungworms (Dictyocaulus viviparus) in calves after previous infections with gastrointestinal nematodes (Ostertagia ostertagi and Cooperia oncophora)

The influence of a priming infection with gastrointestinal nematodes on the subsequent establishment of lungworms was studied. Repeated inoculations of calves with Ostertagia ostertagi and Cooperia oncophora during 3, 5 or 7 weeks resulted in an establishment of lungworms that was 191% of the establishment found in na?ve controls. The higher take was associated with a higher faecal output of lungworm larvae and with lower weight gains of calves. The effect was not significantly influenced by the duration of the primary infections or by the actual presence or absence of worms in the gastrointestinal tract.