A survey of respiratory viruses in New Zealand horses

AIMS: To determine which viruses circulate among selected populations of New Zealand horses and whether or not viral infections were associated with development of respiratory disease.

METHODS: Nasal swabs were collected from 33 healthy horses and 52 horses with respiratory disease and tested by virus isolation and/or PCR for the presence of equine herpesviruses (EHV) and equine rhinitis viruses.

RESULTS: Herpesviruses were the only viruses detected in nasal swab samples. When both the results of nasal swab PCR and virus isolation were considered together, a total of 41/52 (79%) horses with respiratory disease and 2/32 (6%) healthy horses were positive for at least one virus. As such, rates of virus detection were significantly higher (p<0.001) in samples from horses with respiratory disease than from healthy horses. More than half of the virus-positive horses were infected with multiple viruses. Infection with EHV-5 was most common (28 horses), followed by EHV-2 (27 horses), EHV-4 (21 horses) and EHV-1 (3 horses).

CONCLUSIONS: Herpesviruses were more commonly detected in nasal swabs from horses with respiratory disease than from healthy horses suggesting their aetiological involvement in the development of clinical signs among sampled horses. Further investigation to elucidate the exact relationships between these viruses and respiratory disease in horses is warranted.

CLINICAL RELEVANCE: Equine respiratory disease has been recognised as an important cause of wastage for the equine industry worldwide. It is likely multifactorial, involving complex interactions between different microorganisms, the environment and the host. Ability to control, or minimise, the adverse effects of equine respiratory disease is critically dependent on our understanding of microbial agents involved in these interactions. The results of the present study update our knowledge on the equine respiratory viruses currently circulating among selected populations of horses in New Zealand.     

Equine rhinopneumonitis virus infection in New Zealand

Abstract

Extract

Sir,—Japanese workers (Matumoto el al., 1965 Matumoto, M., Ishizaki, R. and Shimuzu, T. 1965. Serologic survey of equine rhinopneumonitis virus infection among horses in various countries. Arch, f. Viruslorsch., 15: 609–624.  [Google Scholar]) have examined 388 horse sera from 17 countries including New Zealand and have found evidence of a high incidence of infection with equine rhinopneumonitis virus. The New Zealand material was supplied between 1957 and 1960, by Dr J. D. Manning, then of the National Health Institute, Wellington.     

A study of neonatal cryptosporidosis of foals in New Zealand

Abstract

AIM: To assess the occurrence of Cryptosporidium oocysts in faecal specimens from foals, and investigate an outbreak of neonatal cryptosporidiosis in foals revealed in the course of the study.

METHODS: Faecal specimens from foals received by a diagnostic veterinary laboratory in New Zealand between 2006 and 2007 were submitted to Massey University and tested microscopically for the presence of Cryptosporidium oocysts. The Cryptosporidium isolates in the oocyst-positive specimens were genetically identified to species level. In addition, specimen submission data from the participating laboratory for 2005–2007 were examined. In the course of the study, the identification of one Cryptosporidium-positive specimen triggered an on-farm investigation.

RESULTS: Twelve faecal specimens submitted by the participating laboratory between 2006 and 2007 were tested further, and three were positive for C. parvum. Specimen submission records indicated a total of 67 faecal specimens were tested for Cryptosporidium by the participating laboratory between 2005 and 2007; 12 (18%) were positive. The on-farm investigation on a broodmare farm revealed a high incidence of neonatal diarrhoea in foals; C. parvum was the only enteropathogen found in the faeces of 4/4 affected foals examined. The diarrhoea in all those foals was self-limiting, manifesting during the second week of life, resembling foal heat diarrhoea, and accompanied by a short but intense period of shedding oocysts.

CONCLUSIONS AND CLINICAL RELEVANCE: The fact that Cryptosporidium parasites were identified in 18% of faecal specimens from foals analysed for this agent in 2005–2007 by the participating laboratory indicated that infection with this agent in foals is not uncommon.

Collectively, the results of this and previous studies performed in New Zealand indicate C. parvum is a cause of diarrhoea in newborn foals, potentially accounting for a proportion of cases empirically diagnosed as foal heat diarrhoea. It is therefore advisable to take precautions when handling diarrhoeic foals, until this potentially zoonotic agent is ruled out in the laboratory.     

Equine hydatidosis: a new record for New Zealand

Cysts found in the liver of a horse which had never been out of New Zealand were used to infect two dogs which were slaughtered 35 days after infection. Large numbers of Echinococcus granulosus were recovered. These cestodes were compared with mature dog-sheep cestodes, using light and scanning electron microscopy and identified as the dog-horse strain of E.granulosus.     

Equine immunity to viruses.

The identification of some of the adaptive immune responses to infection with equine viruses has been the first step toward rational immunoprophylactic design. Sufficient knowledge of infection-induced immunity and informed estimates of the requirements for long-term immunity for EIV have now been obtained. Thus, the future for inactivated EIV vaccines is promising now that new adjuvants have been applied to induce cellular immunity and safe methods have been designed to stimulate virus-neutralizing (VN) antibody at mucosal surfaces. Adenoviruses induce circulating VN antibody, the presence of which appears to correlate with protection from reinfection. Therefore, the potential of vaccines to induce VN antibody and protect from challenge is an important next step with this virus. With persistent viruses such as EHV-1, antibody-mediated protection from infection can be achieved only at the site of initial infection, that is, the nasopharynx and upper respiratory tract. Systemic dissemination is very rapid and consequently VN antibody is unlikely to play a major role in prevention of disease once the initial infection event has occurred. Cellular immune responses, particularly CTLs, play a dominant role in protection and recovery and are important in immune surveillance and determination of the outcome of reactivation of latent virus. Therefore, the key to future EHV-1 vaccine design is to focus on stimulation of CTL responses, and this requires the successful presentation of vaccine-derived antigenic peptides to MHC class I molecules that are recognized by specific receptors on CTL. There is some evidence that stimulation of EHV-1-specific CTL precursors may correlate with immunity to this virus. By analogy with gamma herpesviruses in humans, CTL precursor frequency may also function as an immune correlate for EHV-2. Although EAV infection induces strong immunity in females and geldings, persistent infection of the genital tract is an important route of dissemination from stallions. Although inactivated vaccines induce strong immunity (which depends upon VN activity of serum antibody) to first infection, the immunologic control of persistent infection is currently poorly understood; however, analogy with other persistent viruses suggests that CTLs are also likely to play an important role in the control of persistent EAV infections.     

Isolation of rotavirus from calves, foals, dogs and cats in New Zealand

The incidence of rotaviruses in calves, foals, dogs and cats in the Dunedin urban and rural areas was investigated using electron microscopy and enzyme-linked immunosorbent assays. Of the 283 faecal specimens examined, 26% were positive for rotavirus. Comparison of the genetic electropherotypes was made by separating the viral dsRNA segments using polyacrylamide gel electrophoresis. It is possible that rotavirus infection is a zoonotic disease.     

Cilia-associated respiratory bacillus infection in rats in New Zealand

AIMS: To demonstrate cilia-associated respiratory (CAR) bacillus associated with chronic pneumonia in wild and pet rats in New Zealand. METHODS: A range of tissues from 4 rats were examined grossly and by light microscopy and affected lungs were examined by transmission electron microscopy. RESULTS: All 4 rats had moderate to severe cranioventral bronchopneumonia with bronchiectasis and large numbers of argentophilic bacteria resembling CAR bacillus, intimately associated with the bronchial epithelium. CONCLUSIONS: CAR bacillus infection should be considered as a differential diagnosis for pneumonia in rats in New Zealand.     

A serological survey of canine respiratory coronavirus in New Zealand

ABSTRACT

Aims: To determine the seroprevalence of canine respiratory coronavirus (CRCoV) in New Zealand dogs, and to explore associations with age, sex, breed, month, and geographical region of sampling and reported presence of clinical signs suggestive of respiratory disease.

Methods: A total of 1,015 canine serum samples were randomly selected from submissions to a diagnostic laboratory between March and December 2014, and were analysed for CRCoV antibodies using a competitive ELISA. Logistic regression analysis was used to determine associations between seroprevalence of CRCoV and breed category, age, sex, sampling month, region, and reported health status of dogs.

Results: Overall, 538/1,015 (53.0%) samples were seropositive for CRCoV, with 492/921 (53.4%) positive dogs in the North Island and 46/94 (49%) in the South Island. Age of dog, sampling month, region, and presence of abnormal respiratory signs were included in the initial logistic regression model. Seroprevalence was higher in dogs aged ≥3 compared with ≤2 years (p?<?0.01). The lowest seroprevalence was observed in July (30/105; 28.5%) and August (32/100; 32%), and the highest in June (74/100; 74%). Seroprevalence in dogs from Auckland was higher than in dogs from the Hawkes Bay, Manawatu, Marlborough, and Waikato regions (p?<?0.05). Abnormal respiratory signs (coughing, nasal discharge, or sneezing) were reported for 28/1,015 (2.8%) dogs sampled. Seroprevalence for CRCoV tended to be higher among dogs with respiratory signs (67.9 (95% CI?=?47.6–83.4)%) than dogs with no reported respiratory signs (52.6 (95% CI?=?49.5–55.7)%).

Conclusions: Serological evidence of infection with CRCoV was present in more than half of the dogs tested from throughout New Zealand. Differences in CRCoV seroprevalence between regions and lack of seasonal pattern indicate that factors other than external temperatures may be important in the epidemiology of CRCoV in New Zealand.

Clinical relevance: Our data suggest that CRCoV should be included in investigations of cases of infectious canine tracheobronchitis, particularly if these occur among dogs vaccinated with current vaccines, which do not include CRCoV antigens.     

Equine pituitary pars intermedia dysfunction: current understanding and recommendations from the Australian and New Zealand Equine Endocrine Group

The purpose of this article is to provide a review of the current knowledge and opinions about the epidemiology, clinical findings (including sequelae), diagnosis, treatment and monitoring of equine pituitary pars intermedia dysfunction, particularly in the Australian context. This information and the recommendations provided will assist practitioners in making informed decisions regarding the diagnosis and management of this disorder.     

The isolation of rotavirus from calves,foals, dogs and cats in New Zealand.

The incidence of rotaviruses in calves, foals, dogs and cats in the Dunedin urban and rural areas was investigated using electron microscopy and enzyme-linked immunosorbent assays. Of the 283 faecal specimens examined, 26% were positive for rotavirus.

Comparison of the genetic electropherotypes was made by separating the viral dsRNA segments using polyacrylamide gel electrophoresis. It is possible that rotavirus infection is a zoonotic disease.     

Equine herpesviruses causing respiratory disease

Abstract

Extract

Madam:—I read with interest the letter Fu et al.(3 Fu, Z.F., Robinson, A.J., Dickinson, L.G. and Grimmett, J.B. 1986. Equine herpesvirus type 1 (EHV-1) infection and vaccination with an inactivated EHV-1 vaccine. N.Z. vet. J., 34: 14–15. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]in which they state that “Preliminary investigations on this stud have indicated that equine herpesvirus type 1 (EHV1) and type 2 (EHV2) were frequently isolated and might be the initiators of the respiratory disease observed”. Additional evidence that links EHV2 (equine cytomegalovirus or slowly growing equine herpesvirus) to equine respiratory disease will be important. There is some evidence and a very high level of suspicion that recurrent respiratory disease, malaise and poor performance are associated with EHV2 but providing definite evidence has been elusive and tends to be confounded by the fact that EHV2 can be isolated from more than 70% of horses, in some populations at least, but unassociated with recognisable disease.     

Equine infectious respiratory disease.

During the past 20 years the equine population of Great Britain and Ireland has increased with the result that the practising veterinary surgeon is more frequently called upon to advise on equine problems. A significant portion of this advice is concerned with the examination of horses showing signs of this advice is concerned with the examination of horses showing signs of respiratory disease. Numerous pathogens, which include viruses, bacteria, parasites and moulds invade the respiratory tract causing similar signs of illness. It is therefore difficult to provide an aetiological diagnosis based on a clinical examination. Field studies supported by laboratory investigations have established that influenza and herpes viruses are frequently responsible for outbreaks of disease. Epidemiological studies suggest that other factors including the immune state of the equine population influence the distribution and severity of respiratory disease. The aetiology, diagnosis, treatment and control of equine infectious respiratory disease are discussed below.