Risk factors for highly pathogenic avian influenza in commercial layer chicken farms in bangladesh during 2011.

A case-control study conducted during 2011 involved 90 randomly selected commercial layer farms infected with highly pathogenic avian influenza type A subtype H5N1 (HPAI) and 175 control farms randomly selected from within 5 km of infected farms. A questionnaire was designed to obtain information about potential risk factors for contracting HPAI and was administered to farm owners or managers. Logistic regression analyses were conducted to identify significant risk factors. A total of 20 of 43 risk factors for contracting HPAI were identified after univariable logistic regression analysis. A multivariable logistic regression model was derived by forward stepwise selection. Both unmatched and matched analyses were performed. The key risk factors identified were numbers of staff, frequency of veterinary visits, presence of village chickens roaming on the farm and staff trading birds. Aggregating these findings with those from other studies resulted in a list of 16 key risk factors identified in Bangladesh. Most of these related to biosecurity. It is considered feasible for Bangladesh to achieve a very low incidence of HPAI. Using the cumulative list of risk factors to enhance biosecurity pertaining to commercial farms would facilitate this objective.

Surveillance for avian influenza virus subtypes H5 and H7 in chickens and turkeys farmed commercially in New Zealand.

AIM: To determine the status of avian influenza (AI) virus sub-types H5 and H7 of New Zealand's commercial chicken and turkey farms. METHODS: A cross-sectional serological survey, stratified by production sector, used a sample frame defined by those farms registered with the Poultry Industry Association of New Zealand (PIANZ) or the Egg Producers Federation of New Zealand (EPF). Sectors included were chicken broiler, caged/barn layer, free-range layer, pullet rearer and turkey broiler. The survey used a between- and within-farm design prevalence of 5% (95% confidence for chickens, 99% confidence for turkeys) and 30% (95% confidence), respectively, of AI virus subtypes H5 and H7. The epidemiological unit was the farm for the free-range layer sector, and the individual shed/barn for the other sectors. Serum samples were screened using a commercial generic influenza A indirect ELISA; positive samples were subjected to haemagglutination-inhibition (HI) testing for AI virus subtypes H5 and H7. A comprehensive investigation, that included widespread serological and antigenic screening, was carried out on all farms identified with serum reactors to either the H5 or H7 virus subtype. RESULTS: A total of 4,180 blood samples from 167 chicken and 10 turkey farms were collected and tested using ELISA. Positive ELISA results were returned from 26 farms, comprising 10 caged/barn layer, 14 free-range layer and two turkey (shed-raised) broiler farms. HI testing of ELISA-positive sera for the H7 subtype virus identified no positive sera in any sector. Reactors to the H5 subtype virus were limited to three free-range layer chicken farms; each farm returned a single serum reactor. Follow-up investigations on these free-range farms identified evidence of historic exposure to the H5 subtype virus on one farm, and concluded that the serum reactors identified in the initial sampling round on the other two farms were non-specific (false-positive) reactions. CONCLUSIONS: The survey found no evidence of active infection with notifiable AI viruses, and provided evidence of absence of exposure to AI virus subtypes H5 and H7 in the chicken broiler, caged/barn layer, turkey broiler and pullet-rearer sectors at a between- and within-farm prevalence of 5% and 30%, respectively, with 95% confidence. The results established commercial free-range layer farms as a risk sector for exposure to notifiable AI virus.

Survey of bulk tank milk in New Zealand for Mycoplasma bovis , using species-specific nested PCR and culture.

AIM: To survey the dairy cattle population in New Zealand for the presence or absence of Mycoplasma bovis. METHODS: A random cross-sectional survey of bulk tank milk from dairy herds in New Zealand based on regionally proportioned sampling, weighted towards herds with a high bulk tank milk somatic cell count (SCC) was used to detect M. bovis at a between-herd prevalence of 2%, with 99% confidence. Bulk tank milk samples collected on-farm were tested using a nested M. bovis PCR, and bacteriological culture employing enrichment in mycoplasma broth and direct plating onto mycoplasma agar. RESULTS: Mycoplasma bovis was not detected in any of the 244 bulk tank milk samples by either PCR or culture. CONCLUSIONS: This survey provides further evidence that M. bovis is not present in the dairy cattle population in New Zealand.

Selenium reference ranges in New Zealand cattle.

AIM: To compare serum selenium and liver selenium concentrations with whole blood concentrations in samples taken at the same time from unsupplemented cattle, and to use these comparisons to establish a reference range for use in diagnosing selenium deficiency. METHODS: Selenium was measured in concurrent whole blood, serum and liver samples obtained from cattle in unsupplemented herds in the Manawatu, Waikato and Wairarapa regions of New Zealand. The results were statistically analysed. RESULTS: The revised reference ranges are as follows. [table: see text] CONCLUSION: The serum and liver selenium concentrations used as reference values prior to this study were inaccurate for the detection of selenium deficiency.

Neosporosis in a pup.

CASE: A 13-week-old female boxer pup was found to be suffering from rigidity of the left hindleg. Antibiotic and anti-inflammatory treatment over a 3-week period failed to improve the condition and the pup was humanely killed. METHODS: Serological examination for Neospora antibodies was carried out by the indirect fluorescent antibody test and for Toxoplasma gondii antibodies with a latex agglutination test. A variety of tissues were examined histologically, and the central nervous system by immunohistochemistry and the polymerase chain reaction. RESULTS: The IFAT for anti-Neospora antibodies showed a titre of 1:51 200 in the clinically affected pup while the latex agglutination test for Toxoplasma antibodies was negative. The dam and one of two tested litter-mates had anti-Neospora IFAT titres of 1:1600, the other litter mate was negative. All three were not clinically affected. Histological, immunohistochemical and polymerase chain reaction examinations of the affected pup confirmed the diagnosis of Neospora infection. CONCLUSION: In the live animal, serological examination is thought to be the most useful specific test. Post-mortem examination by traditional histology, immunohistochemistry and the polymerase chain reaction confirmed the diagnosis. The case is discussed in the context of present knowledge about Neospora infection in New Zealand.

A modelling approach to the quantification of the benefits of a national surveillance programme.

A simulation modelling approach was developed to investigate the effects of a reduction in funding for animal health surveillance on the probability of diagnosis of a currently-exotic species of Salmonella if it were introduced into New Zealand. Both severe and mild clinical-disease outbreaks were hypothesized. The probabilities of diagnosis for a single outbreak on a cattle farm under the current surveillance programme were 0.742 and 0.328 for severe and mild clinical-disease episodes respectively, reducing to 0.018 and 0.005 respectively under the reduced surveillance programme. The impacts of these probabilities on the likely time delays from introduction into New Zealand before a definitive diagnosis was reached and the resultant numbers of infected properties were estimated for three different epidemic scenarios. For the best-case epidemic, the median time to diagnosis under the current surveillance programme was 4 weeks (by which time there was still only the index property infected), but under the reduced surveillance programme, the median time to diagnosis was over 1.5 years. Under the most-likely epidemic scenario, the mean time to diagnosis under the current programme was 4 weeks (by which stage there were two infected properties), whereas the median time to diagnosis under the reduced programme was 40 weeks (by which time there were 88 infected herds). With the worst-case epidemic, the median time to diagnosis under the current surveillance programme was still 4 weeks with only two infected properties; however the median time to diagnosis under the reduced programme was 33 weeks by which stage there were 90 infected farms.

Accidental poisoning of a group of yearling cattle by the organophosphate insecticide trichloronat.

Eight yearling cattle were accidentally poisoned with the agricultural organophosphate insecticide trichloronat. One animal showed signs of acute organophosphate poisoning and died. The others showed signs of chronic organophosphate poisoning (organophosphate-induced delayed neuropathy) after 2-3 weeks and one animal died from renal failure at 12 weeks. High levels of trichloronat were measured in fat samples at 6 1/2 weeks. The remaining animals still showed signs of ataxia, possibly due to distal axonopathy, 1 year later but no trichloronat was detected in fat samples at this time.

Neospora abortion in New Zealand cattle.

Protozoal abortion in cattle was retrospectively studied by examining material submitted to the Batchelar Animal Health Laboratory in the years 1987-90. Only cases in which foetal brain had been submitted were examined. Histologically, protozoal lesions were seen in the brains of 28% of 320 aborted foetuses. Lesions were also seen in 10% of the hearts and 34% of the placentas examined, but these were not as characteristic as those in the brains. Protozoa, confirmed immunohistochemically as being Neospora caninum-like in two brains, were seen in 5% of aborted foetuses with lesions. No protozoa or associated lesions were seen in 57 late term foetuses or neonatal controls. A farm survey supported the hypothesis that Neospora is an important cause of multiple abortions in cattle. Laboratory and farm data suggested that protozoal abortion was more common in early gestation. No predisposing causes of abortion were found and there was no evidence of point infection of affected herds.

Citrullinaemia in Friesian calves.

Six Friesian calves from a pedigree herd died or were killed within 1 week of birth because of progressive central nervous disease in which the only consistent lesion was cerebral oedema. The cause was citrullinaemia, resulting from an autosomally inherited dysfunction of the urea cycle enzyme arginosuccinate synthetase. Citrullinaemia was diagnosed by demonstrating markedly elevated concentrations of citrulline in the blood of one calf and in the cerebral spinal fluid of another. One of two sires used in the herd was a heterozygous carrier of the disease. Heterozygocity was demonstrated using a polymerase chain reaction/restriction endonuclease test designed to detect the genetic mutation that causes citrullinaemia in cattle.

Multiple cutaneous histiocytosis in two dogs.

Two cases of canine cutaneous histiocytosis are described. Diagnosis depended on overall consideration of clinical and histopathological features of the disease, as well as its response to anti-inflammatory therapy. No aetiological agent was visible using light and electron microscopy.

The objective interpretation of histopathological data: an application to the ageing of ovine bruises.

Muscle and adipose tissue from a total of 178 experimental bruises inflicted on sheep and aged from 1 to 72 h old were processed for light microscopic examination. Five observed histopathological features of inflammation and repair were scored semiquantitatively on a scale of 1-4 according to their degrees of change from the normal state. These data were evaluated mathematically using a Bayesian probability model designed for the purpose. The model was able to age bruises with an acceptable degree of accuracy only as either 1-20 h or 24-72 h old but within these constraints a degree of confidence in excess of 90% was achieved. The exact performance of the model depended on the nature and number of tissue samples examined but mathematical ageing was superior to interpretative ageing based on personal experience.

A congenital Toxoplasma-like disease in ferrets (Mustela putorius furo).

Approximately 30% of 750 neonatal farmed ferret kits died without observed clinical signs. The presence of multifocal necrosis associated with Toxoplasma-like organisms in the liver, lung and heart suggested a diagnosis of toxoplasmosis. Surviving animals from affected litters were stunted but showed no histological or serological evidence of Toxoplasma infection, nor could infection be demonstrated by mouse inoculation. The involvement of animals at one day of age indicated congenitally acquired disease.