Viruses associated with outbreaks of equine respiratory disease in New Zealand

AIM: To identify viruses associated with respiratory disease in young horses in New Zealand.

METHODS: Nasal swabs and blood samples were collected from 45 foals or horses from five separate outbreaks of respiratory disease that occurred in New Zealand in 1996, and from 37 yearlings at the time of the annual yearling sales in January that same year. Virus isolation from nasal swabs and peripheral blood leukocytes (PBL) was undertaken and serum samples were tested for antibodies against equine herpesviruses (EHV-1, EHV-2, EHV-4 and EHV-5), equine rhinitis-A virus (ERAV), equine rhinitis-B virus (ERBV), equine adenovirus 1 (EAdV-1), equine arteritis virus (EAV), reovirus 3 and parainfluenza virus type 3 (PIV3).

RESULTS: Viruses were isolated from 24/94 (26%) nasal swab samples and from 77/80 (96%) PBL samples collected from both healthy horses and horses showing clinical signs of respiratory disease. All isolates were identified as EHV-2, EHV-4, EHV-5 or untyped EHV. Of the horses and foals tested, 59/82 (72%) were positive for EHV-1 and/or EHV-4 serum neutralising (SN) antibody on at least one sampling occasion, 52/82 (63%) for EHV-1-specific antibody tested by enzyme-linked immunosorbent assay (ELISA), 10/80 (13%) for ERAV SN antibody, 60/80 (75%) for ERBV SN antibody, and 42/80 (53%) for haemagglutination inhibition (HI) antibody to EAdV-1. None of the 64 serum samples tested were positive for antibodies to EAV, reovirus 3 or PIV3. Evidence of infection with all viruses tested was detected in both healthy horses and in horses showing clinical signs of respiratory disease. Recent EHV-2 infection was associated with the development of signs of respiratory disease among yearlings [relative risk (RR)=2.67, 95% CI=1.59-4.47, p=0.017].

CONCLUSIONS: Of the equine respiratory viruses detected in horses in New Zealand during this study, EHV-2 was most likely to be associated with respiratory disease. However, factors other than viral infection are probably important in the development of clinical signs of disease.     

Viruses associated with outbreaks of equine respiratory disease in New Zealand

AIM: To identify viruses associated with respiratory disease in young horses in New Zealand. METHODS: Nasal swabs and blood samples were collected from 45 foals or horses from five separate outbreaks of respiratory disease that occurred in New Zealand in 1996, and from 37 yearlings at the time of the annual yearling sales in January that same year. Virus isolation from nasal swabs and peripheral blood leukocytes (PBL) was undertaken and serum samples were tested for antibodies against equine herpesviruses (EHV-1, EHV-2, EHV-4 and EHV-5), equine rhinitis-A virus (ERAV), equine rhinitis-B virus (ERBV), equine adenovirus 1 (EAdV-1), equine arteritis virus (EAV), reovirus 3 and parainfluenza virus type 3 (PIV3). RESULTS: Viruses were isolated from 24/94 (26%) nasal swab samples and from 77/80 (96%) PBL samples collected from both healthy horses and horses showing clinical signs of respiratory disease. All isolates were identified as EHV-2, EHV-4, EHV-5 or untyped EHV. Of the horses and foals tested, 59/82 (72%) were positive for EHV-1 and/or EHV-4 serum neutralising (SN) antibody on at least one sampling occasion, 52/82 (63%) for EHV-1-specific antibody tested by enzyme-linked immunosorbent assay (ELISA), 10/80 (13%) for ERAV SN antibody, 60/80 (75%) for ERBV SN antibody, and 42/80 (53%) for haemagglutination inhibition (HI) antibody to EAdV-1. None of the 64 serum samples tested were positive for antibodies to EAV, reovirus 3 or PIV3. Evidence of infection with all viruses tested was detected in both healthy horses and in horses showing clinical signs of respiratory disease. Recent EHV-2 infection was associated with the development of signs of respiratory disease among yearlings [relative risk (RR)=2.67, 95% CI=1.59-4.47, p=0.017]. CONCLUSIONS: Of the equine respiratory viruses detected in horses in New Zealand during this study, EHV-2 was most likely to be associated with respiratory disease. However, factors other than viral infection are probably important in the development of clinical signs of disease.     

Viruses associated with feline respiratory disease in Dunedin

Extract

In Dunedin, feline respiratory infections with a high morbidity, but a low mortality except in very young animals, commonly occur in epizootics and appear to be enzootic between these outbreaks. The affected animals develop a serous ocular discharge which later becomes mucoid, and a mucoid nasal discharge associated with sneezing especially after handling. While these signs of infection are present, the animals are anorexic and listless. The disease may last for two weeks or more and sometimes affected cats develop a chronic snuffle lasting for months despite treatment. The disease is usually referred to as “snuffles”, although it is probably identical with the syndrome called “rhinotracheitis”. In the summer time, it commonly occurs in boarding establishments where large numbers of pets collected from a wide area are left by summer vacationers. In breeding catteries, infections occur most often in the spring and especially at the time of the first warm weather. Young kittens about 5 to 10 days old are usually affected but kittens which escape infection at this stage not infrequently develop symptoms at about 6 weeks of age.     

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.     

Caecal intussusceptions in horses: a New Zealand perspective

Objective To establish the prevalence of intussusceptions involving the caecum in a population of horses admitted to a university hospital for colic. Design Retrospective clinical study Methods Medical records of all horses admitted to the Massey University Veterinary Teaching Hospital between 1991 and 2004 were examined for information of those horses diagnosed with an intussusception involving the caecum. Results A total of 135 horses were admitted for colic surgery during the study period and 61 horses had a diagnosis of ileocaecal (37), caecocaecal (5) or caecocolic intussusception (19) made either at surgery or necropsy. Of the horses with ileocaecal intussusception, 32 had an incomplete hand-sewn ileocaecostomy without reduction and 29 survived to discharge. All the horses with caecocaecal intussusceptions were diagnosed preoperatively via rectal examination and/or transabdominal ultrasound: 2 were euthanased at surgery and 3 survived to discharge. In the 19 horses with caecocolic intussusceptions, manually reduction at surgery was performed in 6 and 5 of them survived to discharge. A typhlectomy was performed via a colotomy in 6 horses, 3 of which survived to discharge. Conclusions The high prevalence of intussusceptions involving the caecum seen at this referral centre may indicate a higher prevalence in New Zealand than is reported elsewhere in the world. Clinical relevance Intussusceptions involving the caecum should be considered as a differential diagnosis in horses presenting with chronic low-grade colic. Transabdominal ultrasound is useful for identifying caecocaecal and caecocolic intussusceptions. Hand-sewn side-to-side incomplete ileocaecostomy is a quick, effective and safe method of surgical treatment of ileocaecal intussusceptions.     

The mucolytic effect of Sputolosin in horses with respiratory disease

The effect of the mucolytic drug Sputolosin on the clinical signs of respiratory disease among 28 matched pairs of horses was examined. Compared with the untreated group, the treated group showed a significant decrease in the frequency of coughing and a decreased time to resolution of both cough and nasal discharge. The results indicate that the drug is potentially useful in the management of respiratory disease characterised by an abnormal or increased production of mucus.     

Serum thyroid hormone concentrations in New Zealand horses

Total thyroxine and total tri-iodothyronine concentrations were measured in the sera from 125 horses of mixed age, breed and sex, and varied clinical histories. While low serum thyroxine concentrations were detected in 35 horses, the majority of those horses had serum thyroxine values within the reference range when retested. Only one horse had a mildly decreased serum tri-iodothyronine concentration. Those horses in which the serum thyroxine concentration was low when retested had a normal thyrotropin releasing hormone stimulation test. Hypothyroidism was not diagnosed in any horses in this study. The low serum thyroxine concentrations measured in the present study were attributed to either normal fluctuations in serum concentrations in healthy horses, the effect of drugs, or to the effects of non-thyroidal illness. Because thyroid hormone concentrations are altered by many factors, hypothyroidism should not be diagnosed on the basis of a single low value and further testing, preferably including active stimulation of the thyroid gland, should be carried out.     

Immunopathogenesis and immunotherapy of Culicoides hypersensitivity in horses: an update

Culicoides hypersensitivity (CH) is a strongly pruritic dermatitis of horses, characterised histologically by mixed perivascular to diffuse cellular infiltrates of mononuclear cells and eosinophils, and caused by helper T cell (Th)2, immunoglobulin (Ig)E-mediated reactions to antigens present in the saliva of biting Culicoides midges. As treatment of CH is still not satisfactory, a better knowledge of the pathogenesis of CH is needed for the development of new therapeutic modalities. Accordingly, availability of pure Culicoides allergens instead of crude whole body extracts is essential for the improvement of in vitro diagnosis of CH and development of a more effective allergen immunotherapy (AIT). Beside the Th2 cytokines interleukin (IL)-4 and IL-13, recent studies have shown the involvement of thymic stromal lymphopoietin, IL-5 and IL-31 in the pathogenesis of CH. The importance of IL-5 and IL-31 has been confirmed through targeting these cytokines by active immunisation of CH patients, resulting in a significant decrease of CH lesion scores. Thirty Culicoides salivary allergens have been described over the last 10 years and produced as pure recombinant (r-) proteins. Use of a protein microarray has allowed the identification of the most relevant Culicoides r-allergens for CH in central and northern Europe. An immunisation protocol has been developed for preventive AIT against CH. Small amounts of r-Culicoides allergens injected into the submandibular lymph nodes with Alum/MPLA as adjuvants seem to induce a suitable immune response for both preventive and therapeutic AIT. The next years will reveal whether these recent advancements will translate into an improved diagnosis, treatment and prevention of CH.     

Pasture-associated seasonal respiratory disease in two horses

Two horses on separate farms developed severe obstructive pulmonary disease in successive years during the early summer months. In both cases clinical remission of the respiratory distress was achieved by moving the animals to different environments. The suggested aetiology for this outdoor chronic respiratory disease is a pulmonary allergy to pollen. Both animals were also shown to suffer from classical chronic obstructive pulmonary disease, i.e., obstructive pulmonary disease in the presence of hay and, or, straw.     

Upper respiratory signs associated with Anaplasma phagocytophilum infection in two horses

An adult Quarter Horse gelding (Case 1) was evaluated for tachypnoea and acute dysphagia. A 20-year-old Quarter Horse gelding (Case 2) was evaluated for respiratory stertor and severe, acute swelling of the head in the submandibular region. A physical examination, complete blood count, blood chemistry, upper airway endoscopy, and peripheral blood Anaplasma phagocytophilum polymerase chain reaction were completed for both horses. Both horses tested positive for A. phagocytophilum. The upper airway endoscopy for Case 1 revealed a feed contaminated pharynx, absent swallowing reflex, and left laryngeal hemiplagia. The upper airway endoscopy for Case 2 revealed severe diffuse pharyngeal swelling occluding the airway. Due to increased respiratory effort in Case 2, a tracheotomy was performed. In both horses, treatment consisted of intravenous oxytetracycline 6.6 mg/kg bwt i.v. q. 24 h for 2–3 days followed by minocycline 4 mg/kg bwt per os q. 12 h for 10–14 days. Both horses made full recoveries.     

Foot-and-mouth disease: an assessment of the risks facing New Zealand

Although New Zealand has never had a case of foot-and-mouth disease (FMD), the threat that this disease poses to the economy of this country has long been recognised. The unprecedented global spread of FMD caused by the type-O PanAsia strain, culminating in the outbreak that occurred in the United Kingdom in early 2001, has refocussed the concerns of biosecurity agencies worldwide. The 3 lines of defence against exotic disease incursions in this country are border controls, surveillance and incursion response capability. This article reviews the pathogenesis, virus survival, routes of infection and methods of spread of FMD virus, and in the light of recent international developments, presents a summary of the major risks of introduction and dissemination of FMD virus and the risk-management measures in place for this country.     

Severe respiratory disease in dairy cattle in New York State associated with bovine respiratory syncytial virus infection

Severe respiratory disease associated with bovine respiratory syncytial virus (BRSV) infection has been identified in dairy cattle in New York State. The cases identified occurred in dairy calves and heifers. The disease was characterized in 4 animals by pathologic changes including interstitial pneumonia, necrotizing bronchiolitis with multinucleated syncytial epithelial cells and interstitial emphysema. BRSV antigen was demonstrated in lung samples or was isolated in tissue culture in all 4 cases. A retrospective survey of 6279 bovine diagnostic accessions between 1977 and 1982 revealed 66 cases of interstitial pneumonia, often with concurrent bronchiolitis. In this 5 year period, only 1 case in 1981 had interstitial pneumonia and bronchiolitis with pathologic features consistent with BRSV infection. It is concluded that pathogenic BRSV has entered New York State and that it is contributing to clinical respiratory disease in dairy cattle.     

A cross-sectional survey on wounds in horses in New Zealand

AIM: To determine the frequency and type of skin wounds encountered by New Zealand veterinarians in their equine patients, the duration and estimated costs of treatment as well as the expected outcomes for these wounds.

METHODS: An online survey was sent to all veterinarians registered with the New Zealand Equine Veterinary Association. The survey comprised questions on the location and experience of respondents, the number of wound-related cases in relation to the total equine caseload, the type and anatomical location of wounds treated, the frequency, duration and costs of treatments, the outcome of wound treatment and an estimate of the most common causes of death or euthanasia in their equine patients.

RESULTS: The survey response rate was 110/262 (41.9%). The median number of equine cases seen by respondents was 20 (interquartile range (IQR) 6–60) per month; of these, five (IQR 2–10) were wound related. Wounds ranked third after lameness and respiratory disease for the relative frequency with which respondents encountered them. Of 102 respondents 59 (58%) reported that their clients frequently treated wounds incurred by their horse without consulting a veterinarian. Wounds on the distal limb, whether involving only the skin or also deeper structures, were reported by 86/101 (85%) respondents as the most frequently encountered. Wounds in this location also incurred the longest treatment period and were the most prone to develop complications. Finally, wounds ranked second, after colic, as the most common cause of death/euthanasia in the veterinary respondents’ equine patients.

CONCLUSIONS: The data obtained via the survey indicate that skin wounds, particularly on the distal limb, are a common occurrence in horses in New Zealand and, when they involve structures underlying the skin, are costly and time-consuming to manage and may lead to decreased performance, retirement or euthanasia. Consequently, we recommend that more effort be devoted to the education of equine veterinarians and owners, and that appropriate research funds be allocated to help improve patient outcomes.