The incidence of gastro-intestinal nematodes in cattle in New Zealand

Abstract

Extract

Despite the importance of the beef and dairy industries in this country, little attention has been given to parasitic gastroenteritis as an animal health problem in cattle, although McMeekan (1954 McMeekan, C. P. 1954. Proc. Ruakura Farmers Conference Week, : 186–186.  [Google Scholar]) has stated that helminths are most commonly associated with severe unthriftiness and losses in dairy calves after weaning. Apart from a recent report of a drenching trial in cattle (Cairns and Gallagher, 1964 Cairns, G. C. and Gallagher, R. M. 1964. N.Z. vet J., 12: 26–26. [Taylor &; Francis Online] , [Google Scholar]), there is a complete lack of published information on either the importance and prevalence of the disease in New Zealand, or on the host-parasite relationships concerned in the epidemiology of the disease. Similarly the literature is devoid of data relating to the incidence and distribution of the various parasite species.     

The prevalence of anthelmintic resistance in ovine case submissions to animal health laboratories in New Zealand in 1993

An analysis was undertaken of 177 veterinary diagnostic case submissions to two North Island and two South Island animal health laboratories for faecal egg count reduction testing in sheep during 1993 to provide some comparative data on the frequency of occurrence of anthelmintic resistance. The results suggest that resistance to anthelmintics in sheep nematodes may be more common in the South Island than the North. In both instances this mainly involved resistance to a single drench type, the benzimidazoles. The data indicated a frequency of occurrence of resistance to benzimidazole anthelmintics of 61 and 72%, to levamisole-type anthelmintics of 29 and 29% and to benzimidazole-levamisole combinations of 11 and 22% for submissions to North and South Island laboratories, respectively. In submissions from the South Island, resistance to benzimidazoles involved infections of Nematodirus spp. alone much more frequently than those from the North.     

The prevalence of anthelmintic resistance in ovine case submissions to animal health laboratories in New Zealand in 1993

An analysis was undertaken of 177 veterinary diagnostic case submissions to two North Island and two South Island animal health laboratories for faecal egg count reduction testing in sheep during 1993 to provide some comparative data on the frequency of occurrence of anthelmintic resistance. The results suggest that resistance to anthelmintics in sheep nematodes may be more common in the South Island than the North. In both instances this mainly involved resistance to a single drench type, the benzimidazoles. The data indicated a frequency of occurrence of resistance to benzimidazole anthelmintics of 61 and 72%, to levamisole-type anthelmintics of 29 and 29% and to benzimidazole-levamisole combinations of 11 and 22% for submissions to North and South Island laboratories, respectively. In submissions from the South Island, resistance to benzimidazoles involved infections of Nematodirus spp. alone much more frequently than those from the North.     

The occurrence of anthelmintic-resistant sheep nematodes in the southern North Island of New Zealand

An analysis of veterinary diagnostic cases submitted to the Batchelar Animal Health Laboratory for faecal egg count reduction testing in sheep between 1986 and 1992 showed that 63% of them originated from properties carrying anthelmintic-resistant worms. Most of these cases involved resistance to a single drench type only, with the benzimidazoles being implicated most frequently. Overall, the figures suggested a frequency of occurrence of resistance to benzimidazole anthelmintics of 74%, to levamisole-type anthelmintics of 23% and to benzimidazo-lelevamisole combinations of 30%. No cases of resistance to milbemycin/avermectin-type drenches were recorded.     

Molybdenum and animal health in New Zealand

Extract

Molybdenum is the most recent addition to the group of trace elements that are important in agriculture. In New Zealand it has a special importance, for here it has great possibilities for doing good to animal production, and almost equal possibilities for doing harm. The good comes from improved pasture and crop yields when molybdates are used as fertilizers for deficient soils. The harm is due to stock poisoning by excess molybdenum already present in some pastures or getting there through careless use of molybdate fertilizers.     

The significance of inhibition in the parasitic development of abomasal nematodes in New Zealand sheep

Abstract

Extract

Infective larvae of Haemonchus contortus when ingested by sheep normally undergo development through a series of moults to become sexually mature, adults, a process that takes 14 to 15 days (Veglia, 1915 Veglia, F. 1915. The anatomy and life history of the Haemonchus contortus (Rud). 3rd and 4th Rep. Direct. Vet. Res., Union of South Africa, : 348–500.  [Google Scholar]). In some circumstances, however, such larvae may become arrested in their development at an early fourth larval stage 3 to 4 days following ingestion (Blitz and Gibbs, 1971 Blitz, N. M. and Gibbs, H. C. 1971. Morphological characterization of the stage of arrested development of Haemonchus contortus in sheep. Can. J. Zool., 49: 991–995.  [Google Scholar]). A similar phenomenon of arrested or inhibited development has also been recorded in Ostertagia circumcincta and Trichostrongylus axei infections in sheep; in the former again occurring at an early fourth stage, (Sommerville, 1953 Sommerville, R. I. 1953. Development of Ostertagia circumcincta in the absomasal mucosa of the sheep. Nature. Lond., 171: 482–483.  [Google Scholar], 1954 Sommerville, R. I. 1954. The histotropic phase of the nematode parasite Ostertagia circumcincta. Aust. J. agric. Res., 5: 130–140.  [Google Scholar]) and in the latter at a loosely defined “fourth larval stage” (Reid and Armour, 1972 Reid, J. F. S. and Armour, J. 1972. Seasonal fluctuations and inhibited development of gastro-intestinal nematodes of sheep. Res. vet. Sci., 13: 225–229.  [Google Scholar]).     

Update on the prevalence of anthelmintic resistance in gastrointestinal nematodes of sheep in New Zealand

Abstract

Extract

Recently, a comparison was made between the prevalence of anthelmintic resistance, determined using faecal egg count reduction tests (FECRT), on randomly selected sheep farms in a systematic national survey (Waghorn et al. 2006 Waghorn, TS, Leathwick, DM, Rhodes, AP, Lawrence, KE, Jackson, R, Pomroy, WE, West, DM and Moffat, JR. 2006. Prevalence of anthelmintic resistance on sheep farms in New Zealand. New Zealand Veterinary Journal, 54: 271–277. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) and that derived from similar case material submitted to a veterinary pathology laboratory on a more ad-hoc basis (McKenna 2008 McKenna, PB. 2008. An examination of the relative reliability of laboratory case submissions in determining the prevalence of anthelmintic resistance in sheep nematodes in New Zealand and the possible influence of test analysis methodology on such data. New Zealand Veterinary Journal, 56: 55–59. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). The results of that comparison showed that while there were some differences between them, there were considerable similarities in the prevalence figures obtained from either source. Those similarities, which were particularly evident in terms of the overall pattern of involvement of the various worm genera and the types of anthelmintic concerned, led to the conclusion that FECRT case submissions to veterinary laboratories may offer a useful source of information regarding changes in the prevalence of anthelminticresistant sheep nematodes in New Zealand (McKenna 2008 McKenna, PB. 2008. An examination of the relative reliability of laboratory case submissions in determining the prevalence of anthelmintic resistance in sheep nematodes in New Zealand and the possible influence of test analysis methodology on such data. New Zealand Veterinary Journal, 56: 55–59. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). Accordingly, the present study was undertaken to make further use of this material, to try to ascertain what, if any, such changes may have taken place over the last few years.     

Some problems of animal health in Australia and New Zealand

Extract

My first visit to New Zealand was in 1924, when, immediately after graduating at the Veterinary School of the University of Melbourne, I took up a first appointment to a subsidized practice in the County of Ellesmere. I was then one of fewer than a dozen practitioners, and Government veterinarians were not much more numerous. This period of about two years in practice provided a valuable part of the field experience which is so essential to a research worker. It is again a memorable occasion when, on my return 37 years later, I have the honour to address the New Zealand Veterinary Association comprising some 300 members.     

Enzootic pneumonia of sheep in New Zealand

Extract

Enzootic pneumonia of sheep is a specific condition confined to southern Otago and the Southland district and is commonly referred to as “Southland Pneumonia.” It has been recognized as a distinct clinical entity for many years in that area, heavy losses being reported in the Gore district of Southland in 1924.     

Multiple species of nematodes resistant to ivermectin and a benzimidazole-levamisole combination on a sheep farm in New Zealand

AIM: To confirm the presence of multiple anthelmintic resistance on a sheep farm in New Zealand. METHODS: Three groups of 10 weaned Romney-cross lambs were treated either with an oral dose of ivermectin (0.2 mg/kg), or a benzimidazole/levamisole (BZ/LEV) combination (4.75 albendazole and 7.5 mg/kg levamisole), or were left untreated. Ten days later, animals were necropsied, and adult worms recovered and identified from the abomasa and small intestines. Pre- and post-treatment faecal nematode egg counts (FEC) were recorded, and larval cultures were performed. RESULTS: In a faecal egg count reduction test (FECRT), adjusted to reflect pre- and post-treatment larval culture results, ivermectin resistance was detected in Teladorsagia (Ostertagia), Trichostrongylus and Haemonchus spp, while BZ/LEV combination- resistant Teladorsagia and Trichostrongylus spp were also present. Adult worm counts confirmed these results, and identified the species involved as Teladorsagia circumcincta, Trichostrongylus colubriformis and H. contortus. CONCLUSION: Multiple, multi-generic anthelmintic resistance was confirmed on a sheep property in New Zealand. This included the first confirmed case of ivermectin resistance in T. colubriformis from sheep in New Zealand.     

Scrapie in imported sheep in New Zealand

Extract

The disease known as Scrapie was diagnosed in New Zealand for the first time in June, 1952. Two positive cases and, one suspected case occurred in Canterbury in Suffolk sheep which were imported from England early in 1950. The disease appeared after a typiqally long incubation period and ran a characteristic course in the affected sheep. The outbreak of Scrapie in New Zealand and the drastic measures necessary to control it have placed new emphasis on the difficulty of preventing the introduction of this and other diseases which develop insidiously after a long incubation period, and for which no biological test is available. The same factors have also been responsible for the peculiar difficulties encountered by overseas workers in investigating Scrapie and in establishing clearly the facts of its etiology and transmission.     

Host-parasite checklist of nematodes of domestic ruminants in New Zealand

Extract

Nematodes of domestic ruminants are abundant and widespread throughout New Zealand, and, although the economic importance of some of them is well-recognized, the literature regarding the occurrence, incidence, and distribution of individual species is sparse and very incomplete. A partial explanation of this may be that in diagnostic laboratories in this country, as elsewhere, it is usual for the purposes of routine diagnostic worm counts to identify the parasites at the generic level only. Thus, little information is gained regarding the geographical and seasonal distribution of individual species where more than one species of a genus may occur in the same location in any particular host.     

Multifocal retinitis in New Zealand sheep dogs

Thirty-nine percent of 1,448 working sheep dogs were affected with varying degrees of multifocal retinal disease on ophthalmoscopic examination. Lesions consisted of localized areas of hyperreflexia in the tapetal fundus, often associated with hyperpigmentation. Severely affected animals had widespread hyperreflexia with retinal vascular attenuation. Only 6% of 125 New Zealand dogs raised in urban environment were similarly affected. Both eyes of 70 dogs from New Zealand were examined histologically. Forty-seven of 70 dogs had ocular inflammatory disease. Ten other dogs had noninflammatory eye disease, and 13 dogs had normal eyes. Histologically, eyes with inflammatory disease were divided into three categories: Dogs 3 years of age or less with active inflammatory disease of the retina, uvea, and vitreous. Four dogs in this group had migrating nematode larvae identified morphologically as genus Toxocara. Diffuse retinitis and retinal atrophy in conjunction with localized retinal necrosis and choroidal fibrosis. Dogs in this category were severely, clinically affected. Chronic, low-grade retinitis with variable retinal atrophy. Most dogs in this category were over 3 years of age, and many were visually functional. The existence of a definable spectrum of morphological changes associated with inflammation, suggests that Toxocara sp. ocular larva migrans may be the cause of a highly prevalent, potentially blinding syndrome of working sheep dogs in New Zealand.     

Segmental axonopathy of Merino sheep in New Zealand

AIM: To investigate an axonopathy of Merino sheep that caused progressive hindlimb ataxia and slight to moderate paresis, with the purpose of understanding its pathogenesis. METHODS: Tissues were fixed in buffered paraformaldehyde or paraformaldehyde and glutaraldehyde, processed into wax and epoxy resin, respectively, and examined by light and electron microscopy. Fresh frozen spinal cord and trigeminal nerve roots were subjected to homogenisation, centrifugation and two-dimensional electrophoresis. Selected protein spots were identified using matrix-assisted laser desorption ionisation (MALDI) mass spectrometry. RESULTS. By light microscopy, there were large pale foamy spheroidal axonal swellings affecting peripheral as well as central axons. By electron microscopy, these were shown to contain many membrane-bound vesicles. The main abnormalities in expressed proteins involved cytoskeletal elements and myosin heavy chain, the latter interpreted as associated with the molecular motor myosin Va. CONCLUSIONS: The disorder is the same as that described in Merinos in Australia as segmental axonopathy, and believed to have an inherited aetiology. The lesions and protein changes indicate abnormalities of the cytoskeleton, its relationship with the myelin sheath, and myosin Va molecular motor. The consequence appears to be abnormal axonal transport and inability to maintain the integrity of axons and their myelin sheaths.