Experimental infection of goats with Brucella ovis

Six goats were inoculated with Brucella ovis. Two goats were inoculated with infected semen by the intratesticular route and 2 each by installation of the semen on to the nasal or preputial epithelium. All goats produced antibody responses as measured by an enzyme-linked immunosorbent assay (ELISA) procedure and the serums of 5 goats reacted in complement fixation tests for B. ovis. The 2 goats inoculated by the intratesticular route and one receiving B. ovis instilled intranasally subsequently excreted B. ovis in their semen. The possibility of natural transmission is discussed.     

Effectiveness of a mixture of cyromazine and diazinon for controlling flystrike on sheep

Objective To determine whether there is any need for woolgrowers to add diazinon to cyromazine jetting fluid to control active flystrike on sheep.
Method Larval implants were placed on 143 sheep and allowed to develop for 2 days. Groups of 47 or 48 of these struck sheep were jetted with cyromazine at 1000 mg/L, diazinon at 400 mg/L, or a mixture of the two. After treatment, the implants were assessed daily for 3 days for the presence of feeding larvae.
Results When checked 1 day after treatment, there was a 62% reduction in flystrike in the diazinon treated sheep compared to only 12% reduction on the cyromazine treated sheep. Flystrike reduction on the sheep jetted with the mixture of cyromazine and diazinon was 69%. Three days after treatment flystrike control was 97 to 99% in the latter two groups.
Conclusion Diazinon provided a faster resolution of strikes but by 3 days after treatment there was no significant difference in the number of implants remaining active on the sheep treated with cyromazine or with the mixture of cyro-mazine and diazinon.     

Efficacy of dressings for killing larvae of the sheep blowfly

SUMMARY Resistance to organophosphorus (OP) insecticides in the Australian sheep blowfly has decreased the larvicidal effectiveness of several popular products used as dressings for flystrike. Laboratory bioassays in which near full-size Australian sheep blowfly larvae were immersed in flystrike dressings at registered concentrations for times ranging from 5 to 180 s indicated that none of the products was completely effective in killing highly OP-resistant larvae. Several products performed poorly, even against a susceptible population. Effectiveness did not always reflect the concentration of active ingredient. For example, the products considered to be the most, and least effective overall, contained 0.036% propetamphos but were formulated very differently. Larvicidal efficacy is important in terms of minimising injury to stock but also in the management of insecticide resistance. In situations when the degree of resistance is known, it will be possible to make recommendations for the most cost-effective treatment of flystrike. In the meantime, there appears to be a clear advantage for woolgrowers to use a propetam-phos-based flystrike jetting product to dress flystrike lesions.     

A survey of cattle producers in the Boophilus microplus endemic area of Queensland to determine attitudes to the control of and vaccination against tick fever

SUMMARY: A survey by mail was used to determine the views of beef producers in the Boophilus microplus endemic area of Queensland on the control of and vaccination against tick fever. Data from 448 questionnaires were analysed, representing 2.7% of beef producers in the survey area. Producers considered buffalo fly ( Haematobia irritans exigua ) infestation as the most important problem whereas tick fever ranked sixth overall. Private veterinarians were regarded as the most important source of information on vaccines for cattle followed by a weekly rural newspaper. From the survey we estimate that about 33% of producers used the tick fever vaccine produced by the Tick Fever Research Centre of Queensland Department of Primary Industries but there were significant (P < 0.05) variations between regions and herds. Large herds (≥ 400 head) in south-east Queensland were the most likely to be vaccinated against tick fever. Of the producers who did not use the vaccine, over 70% replied that there was no need to vaccinate because of the low risk of the disease in their herds. In 52% of unvaccinated herds the treatment of animals with acaricide was considered the most important means of tick fever control and 61% of these herds comprised Bos indicus x Bos taurus or Bos indicus cattle.     

Third‐compartment cannulation in alpacas using a polyurethane gastrostomy tube

Objective To develop a simple and effective surgical technique for third‐compartment cannulation in alpacas. Design Prospective study using six adult male alpacas. Methods General anaesthesia was induced and a polyurethane gastrostomy tube was surgically implanted into the distal portion of the third compartment. Results Three of the alpacas retained their cannulas for a 100‐day period; however, three cannulas were dislodged during the study. Two of the three dislodged cannulas were replaced during a second surgical procedure. Cannulas were well tolerated by the alpacas and all animals remained clinically healthy during the study period. Third compartment contents did not leak from the cannulation site. The tubes were manually removed following the completion of the study and the small defect in the body wall quickly healed over in all animals. Conclusion Surgical placement of polyurethane tubes designed for percutaneous endoscopic gastrostomy is a useful method of cannulating the third compartment in camelids. This technique can be used for experimental studies and possibly could be used for nutritional support and fluid therapy in sick camelids that might need long‐term care.     

Isolation and pathogenicity of Australian strains of Eimeria praecox and Eimeria mitis

Objective To determine the presence of E praecox and E mitis in Australia, to isolate representative strains of these species from chickens and determine their pathogenicity.
Design Morphological, physiological and cross protection studies were undertaken to confirm the identity of Australian isolates of E praecox and E mitis.
Procedure Oocysts were isolated from a backyard flock at Jimboomba, southeastern Queensland and numbers of E praecox and E mitis enriched by passage in chickens immune to five other species of poultry Eimeria . Oocysts of mean conformation and size of the two species were purified by single oocyst passage. Two isolates that closely matched recorded parameters for E praecox and E mitis were selected and designated JP and JM respectively. The cross protection between the isolates and E acervulina was determined by infection and challenge experiments. The virulence of the two isolates was determined by comparing weight gains of groups of birds inoculated with JP isolate or JM isolate with untreated groups.
Results Isolates JP and JM most closely matched recorded parameters of E praecox and E mitis respectively. Groups of chickens, previously infected with JP and JM isolates, showed no significant protection against infection with E acervulina . In a separate trial, groups of susceptible chickens inoculated with 10⁵ oocysts of JP and JM isolates showed significantly reduced weight gains compared with untreated controls.
Conclusion Isolates JP and JM are E praecox and E mitis respectively, confirming the presence of these species in Australia. These isolates were found capable of causing significant reductions in weight gains in susceptible chickens.     

Mycobacterium avium subsp. paratuberculosis infection in wildlife on three deer farms with a history of Johne's disease

Abstract

AIM: To determine the prevalence of Mycobacterium avium subsp. paratuberculosis (Map) infection in wildlife, in pastoral landscapes with a recent history of clinical Johne's disease in livestock.

METHODS: A total of 449 wild mammals and birds from three farms in the South Island of New Zealand with recent histories of clinical Johne's disease in their deer herds were trapped and examined for gross pathological changes in the gastrointestinal tract. Additionally, individual mesenteric lymph nodes from 380 mammals, and segments of gastrointestinal tract from 32 birds were excised, homogenised and cultured for viable Map bacilli. The prevalence of Map infection was then calculated for the various species. Faecal samples from those mammals which had culture-positive tissues were further cultured for the presence of Map.

RESULTS: Gross pathological changes were identified in the gastrointestinal tract of four brushtail possums, one cat, six ferrets, 12 hares, six hedgehogs, three rabbits, one stoat, and one paradise shelduck. Infection with Map in the gastrointestinal tract was confirmed in only three of these cases, one each of brushtail possums, hares and hedgehogs. In contrast, Map infection in the absence of gross pathological changes was frequently recorded in enteric tract tissues of mammals and birds. Among mammals, Map infection was recorded in 18/73 (25%) brushtail possums, 4/23 (17%) cats, 15/42 (36%) hedgehogs and 29/113 (26%) rabbits. Among birds, intestinal tract tissue Map infection was recorded in 3/17 (18%) paradise shelducks. Among 64 of the 74 mammals which had Map culture-positive tissues, 38% (n=5) of hedgehogs and 11% (n=3) of rabbits also had culture-positive faecal samples.

CONCLUSIONS: This study is the first to identify that Map infection can be prevalent in wildlife in New Zealand. There was a high prevalence of Map infection among both scavenging and grazing wild animals. Both mammals and birds are capable of harbouring viable Map organisms in their gastrointestinal tract; further, viable Map was excreted into the environment via faeces by hedgehogs and rabbits.

CLINICAL RELEVANCE: Previous studies overseas have postulated a role of wildlife as reservoirs of Map infection and possible vectors of Johne's disease to livestock. Here, brushtail possums, hedgehogs and rabbits and in particular were identified as potential wildlife hosts for Map infection in NewZealand. This suggests that several wildlife species could contribute to the persistence of Map infection within a wildlife/livestock complex, and potentially, perhaps more importantly, to the spread of infection between farms.