Polycystic kidney disease in lambs in New Zealand

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A lethal congenital polycystic kidney disease (PCKD) has been known in lambs in New Zealand for more than 50 years and assumed to be genetic in origin. We have studied this in lambs from an experimental mating in a flock experiencing an outbreak the previous year. Two Perendale rams identified by DNA profiling (SignaGen) as sires of PCKD lambs were each mated to the other's daughters. From 71 such matings, 10 ewes gave birth to 15 PCKD lambs of both sexes. The results are in accord with those expected for a recessive autosomal trait. All lambs were dead or died shortly after birth. Their abdomens were distended by enlarged kidneys 40–140 mm in length. Their cut surface showed a multitude of cystic spaces 1–5 mm in diameter in both the cortex and medulla. Livers of affected lambs showed complex tubular and cystic patterns of bile ducts containing bile, and supported by an excess of fibrous tissue. Cystic changes also occurred in the pancreas and salivary glands.     

The epidemiological control of nematodes in New England lambs

Epidemiological control of nematodes in weaned lambs in New England was investigated over three grazing seasons (n = 58, n = 52 and n = 62 lambs, respectively). Spring prophylactic treatment, clean pasture and mid-summer treat-and-move to hayfield strategies were compared to traditional fall treatments (control). In these studies when lambs were weaned prior to grazing, the most abundant nematodes were Nematodirus sp. Under these conditions, where only low levels of Haemonchus contortus were present, no significant improvement in body weight gain was observed for the epidemiologic approaches compared to the traditional fall treatments. No untreated control was used, and fecal egg counts and pasture larval counts indicate low total worm burdens with a controllable fall rise in pasture infectivity. These results indicate the importance of hypobiosis for the survival of H. contortus and suggest that weaning lambs prior to grazing can be an effective epidemiological control practice.     

Prevalence of dog-derived Sarcocystis spp. in some New Zealand lambs

Pepsin: hydrochloric acid digestion and histological examination of the myocardium of 51 hearts from five to nine month-old lambs from the southern half of the North Island, showed that 47 (92%) were infected with microscopic sarcocysts that are presumed to be dog-derived. Of 157 sarcocysts detected histologically, 32 corresponded morphologically with Sarcocystis ovicanis and 120 with Sarcocystis tenella (Syn. S. arieticanis). The remainder could not be identified as to type.     

Economic effect of pneumonia and pleurisy in lambs in New Zealand

AIM: To estimate the cost of pneumonia and pleurisy in lambs to the sheep industry in New Zealand, in order to provide a reference for future cost-benefit calculations for control programmes to reduce the incidence of pneumonia. METHODS: An estimate of the economic cost of pneumonia and pleurisy in lambs was based on: cohort studies of the association between growth rate and the extent of pneumonic lesions at slaughter (n=14 flocks), the prevalence of moderate to severe (MS) pneumonia (> or =10% lung surface area affected) and pleurisy (n=1,719 flocks), the correlation between the prevalence of MS pneumonia and economic loss at the flock level, and data on annual slaughter statistics and carcass value in New Zealand. A stochastic spreadsheet model was developed and run with 1,000 iterations. Input variables represented by probability distributions were growth rate, average cost of loss according to the prevalence of pneumonia per month, carcass value, prevalence of pleurisy, and carcasses downgraded for pleurisy, and annual national slaughter statistics. The output was a posterior distribution of the annual cost of disease. RESULTS: The cost of pneumonia only included the loss associated with reduced growth rate, while mortality due to pneumonia was assumed to be low and was ignored. The cost of pleurisy included the loss associated with downgraded or condemned carcasses. Thus, the simulated annual average cost of pneumonia was NZ$28.1 (95% CI=NZ$15.0-42.0) million, and that of pleurisy NZ$25.1 (95% CI=NZ$10.2-48.1) million. The combined cost of pneumonia and pleurisy averaged NZ$53.2 (95% CI=NZ$32.4-78.9) million. The parameters with the greatest impact on the combined cost of pneumonia and pleurisy were prevalence of pleurisy between March and May, and cost of reduced growth due to pneumonia for lambs slaughtered in June. CONCLUSIONS: The average cost of pneumonia and pleurisy to the sheep industry in New Zealand due to reduced lamb growth and decreased carcass value is likely to be between NZ$32.4 and $78.9 million. This is a conservative estimate, omitting mortalities, indicating that pneumonia and pleurisy have substantial economic impact on sheep farming in New Zealand. Considering that 23,833,000 lambs were slaughtered in 2003/2004 (average value $65.56/lamb), this cost would equate to NZ$1.36-3.31 per lamb. CLINICAL RELEVANCE: Pneumonia and pleurisy are common diseases in lambs in New Zealand, leading to substantial economic loss to producers.     

A presumed inherited spongiform leucoencephalomyelopathy of Romney lambs in New Zealand

This paper records a unique ovine encephalomyelopathy seen on several farms in the Otago Region of New Zealand. It occurred in 2-3 month-old Romney lambs as a rapidly progressive posterior paresis leading to flaccid paralysis. Pathologically, it was characterised by severe spongy vacuolation of white matter in both brain and spinal cord. It is suspected that the condition is inherited.     

More lambs

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Sir:- The impending release of a drug to enhance ewe fecundity brings the veterinary profession to new horizons of medicine. The implications of the resulting increase in the number of lambs born following the simple technique of injections will place those veterinarians in sheep practice on their mettle. The net effect of treatment is an increased ovulation rate which is reflected by a higher number of lambs. With good management, the end result can be more lambs reared for sale or replacements.     

Lethal osteogenesis imperfecta and skin fragility in newborn New Zealand Romney lambs

Osteogenesis imperfecta and skin fragility occurred in about 50 New Zealand Romney lambs born in a flock of 450 ewes. Affected lambs had soft bones and multiple intrauterine bone fractures. Long bones had a thickened diaphysis with almost complete absence of a medullary cavity. Other consistent gross findings were moderate brachynathia inferior, subcutaneous oedema, marked joint laxity, dark blue sclera and small pink teeth. Histopathologic and ultrastructural changes were consistent with a defect in collagen production by fibroblasts. DNA finger-printing was used to identify which of the five rams used in the flock was carrying the genetic defect. The disease was inherited as an autosomal dominant trait and was considered to be a new mutation in the testicular germ cell lines of this ram.     

Hierarchical and spatial analyses of pneumonia-lesion prevalence at slaughter in New Zealand lambs

We recorded lesions of moderate-to-severe pneumonia (>or=10% lung surface area affected; "pneumonia") in 1,899,556 lambs submitted to three New Zealand abbatoirs between December 2000 and September 2001. The average prevalence of pneumonia ranged between 7 and 13%, by abbatoir. We ran a two-level mixed-effects binomial logistic-regression model with the prevalence of pneumonia as the outcome, and adjusting for abbatoir and month. The intracluster correlations for batch (slaughter lambs from the same farm sent at the same time) and farm were 31.3 and 12.4%, respectively. (We also noted threefold differences in odds across abbatoirs, and >30-fold differences among slaughter months.) Case flocks (those in the upper quintile of pneumonia prevalence) generally were not clustered in the spatial incidence-risk analysis (after adjusting for flock-level and batch level effects, and as compared to flocks in the lower two quintiles). We therefore concluded that the risk of moderate-to-severe pneumonia-lesion prevalence detectable at slaughter of lambs was determined at the flock and batch level, rather than at the spatial level.     

Nephropathy in young lambs

Renal disorders in lambs may be congenital, infectious, toxic, immunologically mediated or secondary to urethral obstruction. Congenital abnormalities are uncommon. Kidney infections often are only one aspect of more widespread diseases, for example, tick pyaemia or salmonellosis. Toxic diseases, which affect mainly the renal tubules, may be caused by bacterial, chemical or plant toxins, although in lamb nephrosis the cause is unknown. Immunecomplex glomerulonephritis is uncommon, and one form, mesangiocapillary glomerulonephritis of Finnish landrace lambs, is under genetic control. Urolithiasis may have secondary effects on the kidneys.     

Microphthalmia in Texel lambs

AIM: To describe an outbreak of congenital microphthalmia in Texel lambs in New Zealand. METHODS: Affected eyes were fixed in 10% formol saline, processed routinely for histopathology and stained with haematoxylin and eosin, Holme's silver and haematoxylin with and without luxol fast blue, and luxol fast blue alone. RESULTS: Macroscopically, the globes and optic nerves were hypoplastic. Histologically, all embryonic components of the eye were present, but the lens, ciliary body, iris and retina were dysplastic. Axons of the hypoplastic optic nerve were poorly myelinated. CONCLUSIONS: Congenital microphthalmia occurs in Texel sheep in New Zealand, and is likely inherited as an autosomal recessive trait.     

Terminal ileitis in lambs

Terminal ileitis was diagnosed in three flocks of lambs in different areas of Alberta. Salient clinical features in affected lambs were progressive emaciation with diarrhea, and in some lambs, frequent abdominal stretching. Postmortem findings included thickening of the ileal, and in some animals, the jejunal, cecal and colonic mucosa as a result of mucosal infiltrates of many lymphocytes and fewer plasma cells, eosinophils, globular leukocytes, and neutrophils. Hyperplasia of intestinal lymphoid tissue was prominent in most affected lambs. The cause of the condition is unknown.