Animal Health Trust
REPORT FOR THE FOURTH QUARTER OF 2002
Equine Viral Arteritis (EVA)
A national serological survey for equine viral arteritis (EVA) is carried out under the supervision of the National Services of Animal Health (SENASA). All the registered stallions must be tested before the next breeding season. Three hundred and eighty-one stallions from 21 different breeds have been checked at INTA Virology Institute. All but 7 of them were seronegative for EVA. The 7 seropositive stallions are Thoroughbreds imported from the United States with an official certificate of EVA vaccination.
During the last four months of 2002, 18 aborted foetuses were submitted to the laboratory for virological studies. None of the abortions could be attributed to viral (EHV-1 or EVA) infection of the foetus.
Cases of respiratory disease in foals were sporadically reported and nasal swabs were laboratory tested but no virus was isolated from them.
No outbreaks of Rotavirus associated diarrhoea have occurred during 2002 foaling season.
There were no clinical cases of influenza within the training Thoroughbred population during this quarter. Influenza vaccination is compulsory in our country and the horses in training at San Isidro racetrack are under a quarterly monitoring programme and have shown good antibody levels.
Equine Herpes Virus
Summary for 2002 breeding season August 1st - December 31st.
Due to duplication of Government, private and Equine Virus Laboratory reporting, there has been some confusion generated about the actual total numbers in the reports received. The position as exists from all agents where results are determined by various testing methods are as follows for the total breeding season for the past 6 months:
1 confirmed case of EHV 1
New South Wales
Samples tested by PCR test in Victoria: 8 samples from 65 horses tested positive.
Samples tested by histopathology in Government laboratory in New South Wales: 18 confirmed cases. However there is some overlap with cases and samples from some horses being tested positive in both the above locations, so the total number of positive cases is less than 26.
Samples tested by PCR in Victoria: 17 positive cases from 78 samples submitted
Samples tested in Victoria Government laboratories: 13 of 49 cases of abortion were positive on histopathology. Again it is uncertain on the degree of overlap of the results. Similarly the real number of positive cases will be less than the total of 30 confirmed cases in all laboratories.
A situation occurred in southern Victoria that recorded multiple cases of abortion early in the breeding season; most have been principally single abortions. A large proportion had a history of travel in late pregnancy, followed by abortion.
The last quarter has seen numerous small outbreaks including 2 in racing stables. The transportation of horses frequently leads to dissemination on small breeding farms where quarantine precautions are not as rigid as on larger farms.
The severe drought in eastern Australia has increased the incidence of strangles due to concentrated numbers of horses during drought feeding. Most cases have had head and neck abscesses.
It continues to be difficult to get information from the provinces as the reporting from the laboratories on non-reportable diseases is only required to be done annually, meaning the reports for 2002 are probably just being compiled.
Equine Herpes Virus
EHV infection was confirmed in three dead standardbred yearlings in Ontario in September by Animal Health Laboratory, Guelph. Four other deaths were suspected as being EHV infection. Five of these seven horses were purchased at a public auction of about 200 yearlings.
Seventy-four cases have been confirmed in horses in Ontario using one or more laboratory tests with a further 26 cases pending results as of 23rd October. Cases were also confirmed in horses in Manitoba and Saskatchewan. A report on the study performed in Ontario is available at www.gov.on.ca.omafra.
Nothing to report
Cases were diagnosed by ELISA on nasopharyngeal swabs from Thoroughbreds in Oise and non-Thoroughbreds (saddler horses and ponies) in Seine et Marne. There were also cases diagnosed by serology in Thoroughbreds in Sarthe and non-Thoroughbreds in Yvelines (saddlers horses and ponies) and in Essonne (ponies).
Equine Herpes Virus
The abortion form was diagnosed by immunofluorescence on cryosections with cell culture and PCR used for confirmation when positive. This form occurred in Thoroughbreds in Calvados.
The respiratory form occurred in Thoroughbreds in Calvados, Oise (in 2 different stables); in saddler horses in Essonne and in ponies in Hauts de Seine.
From November to 23rd December, 86 horses (68 of which died) had signs of ataxia, significant muscle stiffness, depression, dark coloured urine and sweating (without colic and without hypothermia). The sick horses were young, at grass and generally were in the same fields. Death occured between 12 and 72 hours after the start of the illness with 26 localised centres in France detected in the following regions: Ardennes, Calvados, Manche, Marne, Oise, Bas-Rhin, Haut-Rhin, Somme and Val d’Oise. (Similar cases were described in Belgium in 2000 and were described as “atypical myoglobinuria”). There have been no new cases since 30th of November. Investigations into the origin of this condition are in progress.
Nothing to report
There were no cases of equine infectious disease diagnosed in Hong Kong during the fourth quarter of 2002. However during late November and early December, H5N1 avian influenza virus was diagnosed at the Hong Kong Government Veterinary Laboratory and at the University of Hong Kong, as being the causal agent for mortality in waterfowl in a public park (Penfold Park) in the middle of the Hong Kong Jockey Club’s Sha Tin Racecourse. As a result the park was closed for a month, de-populated of waterfowl and the ponds and their environs cleansed and disinfected and the remaining birds sampled. Characterisation of this virus, which has also been sporadically detected in other areas of Hong Kong, has clearly demonstrated it to be different from the H5N1 “Bird Flu” that occurred in the territory in 1997. All horses in the territory exhibiting signs of respiratory tract infection are routinely tested by the rapid diagnostic Directigen Flu-A method with follow-up paired serological tests (for a range of respiratory viruses) and no cases of influenza have been detected. Although there does not appear to be any reports of horses anywhere in the world being infected with avian influenza viruses, naso-pharyngeal swabs of horses with signs of respiratory infection are also periodically submitted to the University of Hong Kong for viral culture.
REPUBLIC OF IRELAND
Regret no report received
Nothing to report.
Contagious equine metritis (CEM)
There were individual cases of CEM on three separate premises on 7th and 22nd October and 25th November. The horses involved were all Thoroughbred breeding stock. The diagnosis was made by PCR.
Nothing to report
Nothing to report
There were 22 notifications of strangles reported throughout the country. Outbreaks continue to be mostly mild and involve all types of horses.
There were 4 notifications of a mild form of influenza.
There were 7 notifications from the Western, North-Western and South-Eastern part of the country between September and the end of November.
There were 8 clinical cases (2 B.caballi, 5 B.equi, 1 B.caballi and equi) and 6 serological diagnoses (5 B.equi, 1 B.caballi and equi) in the Western and Central part of the country. These occurred throughout the reporting period.
One notification of a few ponies in one stable with clinical diagnosis only.
Acute Myopathy in
horses at grass
At the beginning of November, some young horses on different pastures in the Jura suffered from an acute myopathy with symptoms as described by Hosie et al. (1986) and Delguste et al. (2002)
Similar cases occurred in Switzerland in 1989 at the end of October, in the same regions and comparable weather conditions. Most of the horses died or had to be euthanized. One practitioner was convinced that he was able to save some of the horses by administering botulinum antitoxin.
Hosie et al. (1986) Acute myopathy in horses at grass in east and south east Scotland, Vet. Record 119, 444-449
Delguste et al. (2002) Myopathies atypiques chez les chevaux au pré: une série de cas en Belgique, Ann.Méd.Vét., 146, 231-342
Regret no report received
Piroplasmosis (both Babesia equi and Babesi caballi) remains sporadically endemic.
Contagious Equine Metritis (CEM)
A single case in a Warmblood stallion was confirmed on 17th October at the VLA by agent isolation. The stallion had been imported from Germany earlier in 2002. Codes of practice were strictly followed with DEFRA conducting contact tracings and testing. Twenty-four horses were placed under restrictions in November. All semen collected at an affected collection centre has been destroyed.
Disease strain was reported in performance horses (non-Thoroughbred) on 8th November. A Euopean-like strain of equine influenza was confirmed at the Animal Health Trust by agent isolation and nucleoprotein ELISA on nasopharyngeal swabs. The vaccination history of the animals involved was mixed. A small number of horses on 3-4 yards showed clinical signs after mixing whilst hunting. Influenza was confirmed in five horses on three of the premises. Mild signs were seen in vaccinated animals. More severe symptoms (requiring anti-inflammatories and fluid therapy) occurred in some unvaccinated animals. All affected premises were quarantined until two weeks after the last new case.
On 1st December a case was confirmed at the Animal Health Trust by nucleoprotein ELISA on a nasopharyngeal swab from one fully vaccinated non-Thoroughbred performance horse (annual booster vaccination due in February 2003). Very mild signs (slight muco-purulent nasal discharge, short duration pyrexia, cough at rest) were observed in this vaccinated animal. Mild respiratory signs in other horses on the same premises were not confirmed as influenza.
Two separate cases (EHV-1) on 18th November were confirmed at the Animal Health Trust. Diagnosis was by PCR on foetal tissues in the first case and on placental tissues in the second (PCR on foetal tissues was negative in this case). A third case of EHV abortion occurred on 6th December and was confirmed at the Animal Health Trust by positive immunoperoxide staining in conjunction with gross lesions in foetal tissue. The mare was at 213 days gestation and was not vaccinated against EHV. She was housed in a barn with four other pregnant mares, although no other abortions have been reported to date.
Strangles remains endemic in the UK non-Thoroughbred population. Two cases were also confirmed in Thoroughbreds on a single premises (non-racing yard) in October.
Two separate cases of abortion were diagnosed in Thoroughbred mares in central Kentucky during November 2002.
Nile Virus (WNV)
During 2002 WNV has spread across the United States reaching the West Coast states of California and Washington. Presently only Alaska, Arizona, Hawaii, Nevada, Oregon and Utah are considered free of the disease, which is now officially recognized as endemic in the USA. As of December 31, 2002 the Centers for Disease Control (CDC) has reported 3,873 human cases in 39 states plus the District of Columbia, of which 246 were fatal. The epidemic was most intense in the central US especially the Great Lakes region.
As of 31st December, the USDA has reported 14,717 equine cases in 40 states during 2002, of which it is estimated that between 20 to 30% have died or were euthanized. Four states (Illinois, Iowa, Nebraska and Texas) each reported over 1,000 cases.
In addition to the equine and human cases, 14,000 dead birds, primarily crows and blue jays, have been reported, which probably represents a considerable underestimate of the birds that have died from West Nile. The disease has also been implicated in the deaths of several mammalian species including deer, dogs, sheep and goats plus marine mammals including seals and alligators.
INTERNATIONAL COLLATING CENTRE