Epidemic of blindness in kangaroos - evidence of a viral aetiology

OBJECTIVE: To determine the cause of an epidemic of blindness in kangaroos. DESIGN AND PROCEDURES: Laboratory examinations were made of eyes and brains of a large number of kangaroos using serological, virological, histopathological, electron microscopical, immunohistochemical methods, and PCR with cDNA sequencing. In addition, potential insect viral vectors identified during the disease outbreak were examined for specific viral genomic sequences. SAMPLE POPULATION: For histopathological analysis, 55 apparently blind and 18 apparently normal wild kangaroos and wallabies were obtained from New South Wales, Victoria, South Australia, and Western Australia. A total of 437 wild kangaroos and wallabies (including 23 animals with apparent blindness) were examined serologically. RESULTS: Orbiviruses of the Wallal and Warrego serogroups were isolated from kangaroos affected with blindness in a major epidemic in south-eastern Australia in 1994 and 1995 and extending to Western Australia in 1995/96. Histopathological examinations showed severe degeneration and inflammation in the eyes, and mild inflammation in the brains. In affected retinas, Wallal virus antigen was detected by immunohistochemical analysis and orbiviruses were seen in electron microscopy. There was serological variation in the newly isolated Wallal virus from archival Wallal virus that had been isolated in northern Australia. There were also variations of up to 20% in genotype sequence from the reference archival virus. Polymerase chain reactions showed that Wallal virus was present during the epidemic in three species of midges, Culicoides austropalpalis, C dycei and C marksi. Wallal virus nucleic acid was also detected by PCR in a paraffin-embedded retina taken from a blind kangaroo in 1975. CONCLUSION: Wallal virus and perhaps also Warrego virus are the cause of the outbreak of blindness in kangaroos. Other viruses may also be involved, but the evidence in this paper indicates a variant of Wallal virus, an orbivirus transmitted by midges, has the strongest aetiological association, and immunohistochemical analysis implicates it as the most damaging factor in the affected eyes.     

Polymerase chain reaction and other laboratory techniques in the diagnosis of long incubation rabies in Australia

SUMMARY Blood and post-mortem tissues from a 10-years-old girl were submitted to the Australian Animal Health Laboratory. Clinical signs and histopathological lesions had suggested a diagnosis of rabies, but, an unusually long incubation period of at least 5 years did not encourage such a diagnosis. Serological examinations by the rapid fluorescent focus inhibition test revealed a dramatic increase in rabies virus-neutralising antibody during the 10-day period of hospitalisation. The results of a fluorescent antibody test on brain smears, and an immunoperoxidase test on formalin-fixed sections of brain were also consistent with a diagnosis of rabies. Attempts to isolate virus were unsuccessful. Polymerase chain reactions (PCRs) were conducted on a 10% suspension of a post-mortem sample from the patient's brain, using primers based on the published sequence of the Pasteur virus strain of rabies virus. 413 and 513 bp fragments from the nucleoprotein gene and a 403 bp fragment from the glycoprotein gene were amplified. Subsequent sequencing of these fragments, and comparison with equivalent regions of known rabies viruses, confirmed that the fragments originated from a virus belonging to the rabies virus serotype. This case demonstrated the advantage of using a range of laboratory techniques to obtain a definitive diagnosis. In particular, a PCR-based test may allow a diagnosis, even in the face of conditions that preclude virus isolation such as apparently occurred in this case. Finally, this case demonstrated that an unusually long incubation period should not discourage a tentative clinical diagnosis of rabies.     

A non-invasive technique for standing surgical repair of urinary bladder rupture in a post-partum mare: a case report

An 11-year-old mare presented 36 hours after foaling with a ruptured bladder. Uroperitoneum was diagnosed on ultrasound and from the creatinine concentration of the peritoneal fluid. Bladder endoscopy demonstrated tissue necrosis and a rent in the dorsocranial aspect of the bladder. Following stabilisation, including abdominal drainage and lavage, the mare was taken to standing surgery. Under continuous sedation and epidural anaesthesia, and after surgical preparation, a Balfour retractor was placed in the vagina. Using sterile lubricant and moderate force, it was possible to insert a hand into the bladder. The tear was easily palpable on the dorsal portion of the bladder. Two fingers were inserted through the tear and used to provide traction to evert the bladder completely into the vagina where it could grasped with the surgeons other hand to prevent further trauma. A second surgeon could then visualise the entire tear and repaired this using a single layer of size zero PDS suture in a single continuous pattern. As soon as the bladder was repaired, it was replaced via the urethra. The mare did well after surgery and was discharged after 48 hours, apparently normal.This report is the first describing repair of the bladder without an abdominal incision or incision into the urethral sphincter. This greatly reduces the chance of possible complications such as urine pooling after surgery with the previously described standing technique or bladder trauma due to traction with abdominal surgery.     

Factors affecting the breeding success of the African Black Oystercatcher (Haematopus moquini): a perspective on protection and food availability

Breeding success (fledglings pair^?1 y^?1) of the Red-listed African Black Oystercatcher (Haematopus moquini) is highly variable, both spatially and temporally. Despite a diversity of natural factors causing this variability, there is evidence that two anthropogenic factors, i.e. disturbance and an introduced mussel (Mytilus galloprovincialis), are having an impact on the local breeding success of this species. Using a data set comprising 87 site-years of nest-monitoring data across most of the species’ breeding range, we analysed the extent and causes of variability in breeding success. Breeding success differed across three population categories defined by varying levels of human disturbance: island populations, protected mainland populations, and unprotected mainland populations. Differences in breeding success between island populations and protected mainland populations were likely due to differing exposure to predators; however, differences between protected and unprotected mainland populations were unlikely caused by this as both experience equivalent predation levels (although from different predators). Protection only improved the breeding success of oystercatchers in very high-quality habitats (with a high biomass of alien mussels), and where populations were ‘released’ from high levels of human disturbance. In unprotected mainland areas, human activity impacted on the breeding success of local populations primarily through predation of small chicks by uncontrolled dogs, and by rising tides drowning chicks that were hiding from human disturbance. The findings of this study note the potential conservation dilemma resulting from an invasive species improving the conservation status of a Red-listed species, and encourage the implementation of restricted sites in high-quality habitats with high breeding pair densities.     

SNP g.1007A>G within the porcine DNAL4 gene affects sperm motility traits and percentage of midpiece abnormalities

The flagellar beating of a spermatozoa's axoneme is caused by the varying activation and inactivation of dynein molecules. Dynein, axonemal, light chain 4 (DNAL 4 ) is a functional candidate gene for sperm motility as it encodes a small subunit of the dyneins. We resequenced the porcine DNAL 4 using three artificial insemination (AI ) boars each with high (>68%) or low (<60%) motility, and detected 23 SNP . These were then genotyped for 82 AI boars. Using spermatological records, significantly negative genetic correlations between ejaculate volume (VOL ) and the further spermatological parameters concentration (CONC ) (r  = ?.43), motility of undiluted semen (MOTUD ) (r  = ?.09), motility after 24 h (MOT 1) (r  = ?.17) and after 48 hr (MOT 2) (r  = ?.23) were estimated. Significantly positive correlations existed between CONC and MOT 1 (r  = .07) as well as MOT 2 (r  = .10), between MOTUD and MOT 1 (r  = .33), between MOTUD and MOT 2 (r  = .36), and finally between MOT 1 and MOT 2 (r  = .70). Significantly negatively correlated were all motility traits with the parameters abnormal acrosome (AA ) (MOTUD r  = ?.06; MOT 1 r  = ?.08, and MOT 2 r  = ?.1) and presence of cytoplasmic droplet (CD ) (MOTUD r  = ?.07; MOT 1 r  = ?.08; MOT 2 r  = ?.07). Association analyses (single marker regression model; SMR ) propose that SNP g.1007A>G, located in the second intron, reduces motility significantly (MOTUD ‐4.59%; MOT 1 ‐10.33%; MOT 2 ‐19.37%). According to the dominant‐recessive model (DRM ), genotype AA is always superior compared to genotypes AG and GG (i.e. MOTUD 67.67%, 64.16% and 53.91%; MOT 1 54.17%, 43.75% and 28.44%; MOT 2 44.12%, 24.91% and 4.97%). The average effect of gene substitution (g.1007A>G) on abnormal midpiece (AM ) was 0.71%, the genotypic values—as expressed by LS means—were 0.1 (AA ) and 0.81 (AG ).     

Congenital polycystic kidney disease in lambs

AIM: To describe the pathology and inheritance of a congenital polycystic kidney disease (PKD) of sheep.

METHODS: Mode of inheritance of PKD was investigated by evaluation of results of the disorder from planned matings in two consecutive years within subsets of a flock that had a high prevalence of PKD in lambs. Gross pathological and histopath- ological studies were based on tissues derived from this study. Haematoxylin and eosin (H&E)-stained paraffin sections of kidney, liver, extrahepatic biliary and pancreatic ducts, pancreas and epididymis were used to describe the lesions.

RESULTS: Twenty-five lambs affected by PKD, of both sexes, were born, numbers in accord with those expected for an autosomal recessive disorder in the population studied. In all cases for which tissues were available, the renal, bile ductal (intrahepatic and extrahepatic), pancreatic and epididymal tissues had widespread dysplastic changes and associated cyst formation.

CONCLUSIONS: The findings of renal cysts in conjunction with cysts in other organs are unifying features in many of the human and animal forms of PKD and suggest a related pathogenic and genetic base consistent with an autosomal recessive disorder.     

A critical evaluation of serum methylmalonic acid and vitamin B12 for the assessment of cobalt deficiency of growing lambs in New Zealand

AIM: To derive reference ranges for serum methylmalonic acid (MMA) for the diagnosis of cobalt/vitamin B₁₂-responsiveness in lambs and critique existing serum vitamin B₁₂ reference ranges.

METHODS: Individual animal data from earlier supplementation trials, involving 225 ewes, 106 suckling lambs, 301 lambs during the suckling and post-weaning periods and 414 weaned lambs, for which weight gain to supplementation was observed, were used to derive relationships between serum vitamin B₁₂ and MMA, and liveweight gain.

RESULTS: Serum MMA concentrations were rarely elevated above the norm of <2 µmol/L when serum vitamin B₁₂ concentrations were >375 pmol/L, and not elevated into the range where a liveweight response to supplementation occurred (>10 µmol/L) unless serum vitamin B₁₂ concentrations were below 200 pmol/L. Suckling lambs were able to maintain high growth rates despite elevated serum MMA concentrations (>20 µmol/L).

CONCLUSIONS: The current reference ranges used in New Zealand for serum vitamin B₁₂ are set conservatively high. Serum MMA concentrations appear to allow better differentiation of a responsive condition than vitamin B₁₂ concentrations. Serum MMA concentrations <13 µmol/L indicate responsiveness to supplementation whilst concentrations <7 µmol/L indicate unresponsiveness. In the range 7–13 µmol/L, variation in response was observed and predictability of response is less certain, but supplementation is advisable.

CLINICAL RELEVANCE: The current reference ranges for vitamin B₁₂ responsiveness are conservatively high and lead to over-diagnosis of vitamin B₁₂ deficiency in ill-thriftiness of sheep.