Metastatic mineralisation in brushtail possums (Trichosurus vulpecula) from Kawau Island

AIMS: To describe the nature and incidence of metastatic mineralisation in brushtail possums (Trichosurus vulpecula) caught on Kawau Island. METHODS: Wild-caught possums were individually housed in captivity over a 24-month period and fed a cereal-based mash diet. Possums that became debilitated were examined post mortem for evidence of metastatic mineralisation of the heart, major blood vessels and kidneys. Serum and aortic segments were collected from affected animals and were analysed for mineral composition. Non-debilitated animals and possums that were experimentally poisoned with cholecalciferol were examined as a comparison. RESULTS: Fifteen of 42 possums (36%) captured on Kawau Island and housed in captivity were debilitated as a result of metastatic mineralisation of the walls of the aorta and/or of the kidney tubules, with four further possums having evidence of mineralisation when humanely killed. Phosphate and ammonium deposits were found in the aorta, and calcium deposits in the kidney tubules. Serum phosphorus and calcium levels were elevated in the debilitated animals. Similar lesions were found in only one of 288 possums captured from other North Island areas and housed in captivity over the same time period. CONCLUSION: Possums from Kawau Island appear to be more predisposed to metastatic mineralisation than possums from other areas of the North Island. The lesions observed in these possums were similar to those caused by cholecalciferol poisoning.     

Resistance to a triple-combination anthelmintic in Trichostrongylus spp. on a commercial sheep farm in New Zealand

Abstract

AIM: To evaluate resistance to anthelmintics containing abamectin, levamisole, and oxfendazole (AB-LEV-OX), derquantal and abamectin (DEQ-AB), moxidectin, and monepantel in naturally acquired gastrointestinal nematodes present on a sheep farm.

METHODS: Faecal nematode egg count reduction tests (FECRT) were carried out on lambs that were approximately 7 months-old and infected with naturally acquired nematodes. Lambs were randomly allocated to one of five groups (n=15 per group): treatment with 2?mg/kg derquantel and 0.2?mg/kg abamectin; 0.2?mg/kg abamectin, 8?mg/kg levamisole HCl and 4.5?mg/kg oxfendazole; 2.5?mg/kg monepantel; 0.2?mg/kg moxidectin, or no treatment. Post-treatment samples were collected 12 days later. Abomasa and small intestines were collected from two slaughtered lambs from each of the DEQ-AB, AB-LEV-OX, moxidectin and control groups 15 days after treatment, for nematode counting.

RESULTS: The FECRT demonstrated that efficacy was 90.3 (95% CI=84.2–94.1)% for AB-LEV-OX, 54.5 (95% CI=28.4–71.1)% for moxidectin, 99.2 (95% CI=97.4–99.8)% for DEQ-AB and 100% for monepantel, across all genera. For Trichostrongylus spp. efficacy was 85.5% for AB-LEV-OX and 46.7% for moxidectin. Haemonchus spp. were fully susceptible to all treatments. Post-treatment nematode counts indicated that the resistant Trichostrongylus spp. were from the small intestine.

CONCLUSIONS: Anthelmintic resistance to both AB-LEV-OX and moxidectin was present in the Trichostrongylus genus on a commercial sheep farm. Monepantel and DEQ-AB were both effective against Trichostrongylus spp. based on FECRT results.

CLINICAL RELEVANCE: This finding of resistance to an AB-LEV-OX triple-combination anthelmintic in the Trichostrongylus genus in sheep in New Zealand further limits anthelmintic treatment options available, and calls into question whether this combination is suitable for use as a quarantine treatment.     

Intramyocardial haematoma causing right ventricular outflow obstruction after brown snake (Pseudonaja species) envenomation in a dog

A 15-month-old, male neutered Staffordshire Bull Terrier cross was presented to its referring veterinarian collapsed and agonal. He was immediately intubated, manually ventilated, and treatment commenced for presumptive snake envenomation with two vials of Tiger/Multi-Brown Snake Antivenom (minimum 7000 units/vial). The dog was transferred to a referral hospital intubated. Additional diagnostics performed following arrival at the referral hospital included a urine snake venom detection kit test, which was positive for brown snake immunotype. Three additional vials of Tiger/Multi-Brown Snake Antivenom (minimum 7000 units/vial) were administered until the dog was extubated and able to stand. Venom-induced consumptive coagulopathy (VICC) was diagnosed based on prolonged clotting times and scleral haemorrhage. Paroxysms of right ventricular outflow tract (RVOT) origin ventricular arrhythmias were treated with lignocaine and sotalol. Four days after presentation, a new-grade IV/VI systolic heart murmur was auscultated, prompting an echocardiogram. An anechoic and compartmentalised mass measuring 43 mm × 19 mm was visualized within the right ventricular wall at the RVOT, immediately adjacent to the pulmonic valve. The mass was causing a RVOT obstruction. Its appearance was suggestive of an intramyocardial haematoma, most likely secondary to VICC. The dog remained cardiovascularly stable, and treatment consisted of supportive care. Recheck echocardiograms at 2 and 7 weeks after discharge revealed progressive improvement of the intramyocardial mass and resolution of the associated heart murmur. Although intramyocardial haematomas are rare, it should be considered as a differential in dogs that develop a newly diagnosed heart murmur and/or cardiac arrhythmia following brown snake envenomation.     

Scrotal circumference,bodyweight and semen characteristics in growing dairy-breed natural-service bulls in Tasmania,Australia

Aims: To provide herd managers with a set of decision rules allowing them to predict the likelihood that a juvenile bull is ready for Bull Breeding Soundness Evaluation (BBSE), or breeding, if bodyweight and scrotal circumference are known.

Methods: This was a longitudinal study following two groups of young pasture-fed Holstein and Jersey bulls from northwest Tasmania, Australia. Individual scrotal circumference, bodyweight and semen characteristics were recorded at 6–8 weekly intervals, from 6–18 months of age. Classification and regression tree analyses were used to predict the probability that a bull had ≥70% normal sperm morphology based on scrotal circumference and bodyweight measurements.

Results: Overall 1,661 scrotal circumference and bodyweight measurements were obtained, and 518 semen samples from 356 bulls were assessed for sperm morphology, from 16 examination sessions that took place between 29 May 2015 and 17 August 2016. Classification and regression tree analyses generated a decision tree for Holstein bulls with four node endpoints, and for Jersey bulls with three node endpoints. Diagnostic test performance showed that for Holstein bulls, using the node endpoints of scrotal circumference ≥27?cm and bodyweight ≥349?kg, 98% had ≥70% normal sperm (positive likelihood ratio 10.4; 95% CI?=?2.7–41), and using the node endpoints of scrotal circumference ≥27?cm and bodyweight between 282–349?kg, 89% had ≥70% normal sperm (positive likelihood ratio 1.6; 95% CI?=?0.9–2.6). For Jersey bulls, using the node endpoints of bodyweight ≥259?kg and scrotal circumference ≥29?cm, 88% had ≥70% normal sperm (positive likelihood ratio 3.4; 95% CI?=?1.6–7.0).

Conclusions: This study provides a set of relatively simple decision rules based on bodyweight and scrotal circumference measurements that allows herd managers to assess the likelihood that juvenile bulls are ready for BBSE or breeding.

Abbreviations: BBSE: Bull breeding soundness evaluation; BRT: Boosted regression tree     

Molecular and serologic characterization, pathogenicity, and protection studies with infectious bronchitis virus field isolates from California

In this study, we characterized three variant infectious bronchitis virus (IBV) strains isolated in 2003 and 2004 from broiler chickens in California and compared them to previously isolated California variant viruses and to common vaccine serotypes used in the United States. We conducted genetic, serologic, and pathogenicity studies on all three isolates, then tested different vaccines against one of the viruses. Genetically the three variant IBV strains, designated CA557/03, CA706/03, and CA1737/04, were not related to each other. GenBank BLAST database search and phylogenetic analysis of the hypervariable region of the S1 subunit of the spike gene to determine the most closely related viruses to the three variants showed the CA557/03 variant to be 81.8% similar to the CAV/CA56b/91 whereas the CA706/03 and CA1737/04 variant viruses were only distantly related to Dutch/D1466/81 (72.2%), a vaccine strain used in Europe, and Korea/K142/02 (72.7%), a Korean field isolate, respectively. Cross virus-neutralization testing showed that none of the 2003-04 California IBV variant viruses were serologically related to each other or to Ark, Conn, or Mass vaccine strains. In addition the CA1737/04 isolate was also tested against DE072 and found not to be serologically related. All three variant viruses were pathogenic in 1-wk-old broilers and vaccination with Mass/Conn followed by Holland/Conn provided 80% protection against the CA1737/04 virus. The 2003-04 California variant viruses were not compared with variants isolated in California during 1970s and 1980s because, to our knowledge, no genetic information is available and those viruses are no longer obtainable. This study shows that the CA557/03 virus was distantly related to the CAV-type viruses isolated in California in the early 1990s, but that none of the 2003-04 viruses were similar genetically or serologically to the CAL99-type viruses, indicating that new IBV variants continue to emerge and cause disease in commercial chickens in California.     

Evaluation of the effectiveness of two infectious bronchitis virus vaccine programs for preventing disease caused by a California IBV field isolate

Infectious bronchitis virus CA99 serotype was isolated from several broiler flocks in Northern California. The virus caused late-onset respiratory disease and increased airsacculitis condemnation in affected flocks despite the use of an established infectious bronchitis virus vaccination program. An experimental study compared Holland/Arkansas and Massachusetts/Arkansas vaccination protocols to determine the efficacy of commercial infectious bronchitis virus vaccines in reducing respiratory disease and airsacculitis lesions found at processing that were associated with a CA99 field isolate. All vaccination groups were given Massachusetts/Connecticut strains of infectious bronchitis virus vaccines at age 1 day followed by vaccination with either Holland/ Arkansas or Massachusetts/Arkansas vaccine strains at 18 days of age. Birds were challenged at age 31 days with a CA99 field isolate. Gross pathology, histopathology, and virus isolation were evaluated. Chickens vaccinated with Holland/Arkansas had marginally better protection against CA99 challenge than chickens vaccinated with Massachusetts/Arkansas, although differences were not statistically significant.