Companion May 2012 - BSAVA

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Notifiable and zoonotic disease for companion animal practitioners ■■ More than half of households keep pets, and even among those who do not own companion animals the majority will have direct (animal) or indirect (e.g. faecal) contact with a companion animal at some time*. ■■ Animals share our homes, and often our kitchens and bedrooms, increasing the risk of disease transmission*. ■■ The introduction of the Pet Travel Scheme has led to a significant increase in pet travel. This is likely to increase further following the reduction in regulation and quarantine after 1st January 2012. The increase in movement of companion animals increases the risk of introduction of ‘exotic’ and potentially zoonotic disease. ■■ The increasing tendency to keep ‘exotic pets’ also carries implications for the spread of zoonotic disease*. There are a wide range of diseases which can theoretically be transmitted from animals to humans; further details can be obtained from the Health Protection Agency website (http://www.hpa.org.uk/ Topics/InfectiousDiseases/ InfectionsAZ/Zoonoses/ TableZoonoticDiseases). Examples of zoonotic disease Salmonellosis Infection may occur in all animals and is usually acquired through contact with contaminated food or water or from exposure to infected faecal material. It should be noted that Salmonella spp. have been isolated from a wide range of species kept as pets, possibly as components of the natural flora, from rodents, reptiles and birds. While acute gastroenteritis is the most common manifestation of infection, septicaemia may also develop. Enteric salmonellosis is self-limiting and antibiotics are not indicated in uncomplicated cases. Animals with septicaemia will require intensive care including fluid therapy and appropriate antibiotic therapy. Of particular 10 | companion note in guinea pigs, salmonellosis typically manifests as septicaemia and death rather than enteritis and diarrhoea. Lymphocytic choriomeningitis Lymphocytic choriomeningitis virus (LCM) is an RNA Arenavirus that causes a chronic fatal wasting of young hamsters. Wild mice are a common primary reservoir of infection but hamsters and guinea pigs can also act as reservoirs. The disease may also be seen in chinchillas and chipmunks. Diagnosis is by PCR, serological detection of anti-LCMV antibodies or virus isolation. Humans may become infected by exposure to urine and faeces or from a bite. In most human cases symptoms are flu-like: headaches, fever, myalgia or arthritis. Rarely a fatal aseptic meningitis or meningoencephalitis develops. As well as considering disease in animals we have to consider the health implications for ourselves, and our staff, of contact with zoonotic diseases which may require reporting under the Reporting of Injuries, Diseases, and Dangerous Occurrences Regulations, 1995 (RIDDOR). These include: ■■ Anthrax ■■ Brucellosis ■■ Chlamydiosis ■■ Leptospirosis ■■ Lyme disease ■■ Q fever ■■ Rabies ■■ Tuberculosis. Further information can be obtained from http://www.hpa.org.uk. Companion animal notifiable disease Rabies Classical rabies was eradicated from the UK in 1922. It is thought that our island status makes it unlikely that terrestrial rabies will be re-introduced through wildlife and that the largest risk for rabies entering the UK would be through an infected animal imported into the country illegally. The last case of rabies in an animal outside of quarantine in the UK was a dog in Camberley in 1970 and the last case of rabies in quarantine was reported in 2008. The Pet Travel Scheme (PETS) was launched in 2000 to allow people to travel with their pets while ensuring the UK remains free from rabies and certain other exotic diseases. In total, 752,945 pet animals have entered the UK under PETS since 2000 (ferrets have only been able to enter under the scheme since July 2004), and there have been no cases of rabies in any of these animals (Defra, 2010). However, since 2001 nine rabid dogs have been illegally introduced into France; all but one of these was imported from Morocco through Spain. Rabies has also been reported in individual animals in Norway and The Netherlands, indicating that illegally imported dogs continue to pose a risk of rabies in otherwise rabiesfree regions. Defra have admitted that the changes to the pet travel regulations that came into effect on 1st January 2012 do increase the risk of rabies being introduced to the UK. However their risk assessment suggests that the risk is still very small, calculated to be one rabies introduction every 211 years, or one rabies case for 9,809,601 animals imported, although these figures assume 100% compliance with the regulations (VLA 2010). EBLV Cases of bats infected with one of the two European Bat Lyssavirus (EBLV) subtypes have been confirmed in the UK as recently as 2009. One of these cases resulted in the death of a bat worker in Scotland in November 2002. EBLV is transmitted through contact with an infected bat, for example through bites, scratches or saliva. All reported cases in the UK have so far occurred in Daubenton’s bats (Myotis daubentonii), a common species which often comes into human contact as it roosts in houses.
Up to 8% of Daubenton’s bats carry antibodies to the virus. A novel lyssavirus has recently been reported in a Natterer’s bat in Germany. It is very rare for EBLVs to cross the ‘species barrier’; however EBLV-1 has infected other animals, including five sheep in Denmark, a stone marten in Germany, and two cats in France. Classical rabies has never been recorded in a native European bat species. Defra takes a precautionary approach to possible contacts with bats by bat workers and others handling bats on a routine basis, as well as any incident where a member of the public has come into contact with a bat. The Health Protection Agency (HPA) has detailed guidance, which includes recommended pre-exposure vaccination for those handling bats, and immediate precautionary administration of rabies vaccine for anyone bitten or scratched by a bat. In light of the HPA guidance, it is not automatically necessary to euthanase a healthy bat for rabies testing involved in a biting or scratching incident. However, any bat suspected of being infected with EBLV must, by law, be reported to the AHVLA. Readers are directed to the “How to handle bats” article in companion June 2009 for more information. Notifiable diseases of other animals that may affect pets Although rabies is the only notifiable disease which normally affects dogs and cats, it should be remembered that dogs and cats can sometimes become infected with other notifiable diseases. Avian influenza There have been no cases of avian influenza reported in dogs, but there are a small number of confirmed cases in cats. It is thought that cases of H5N1 infection in cats have resulted from prior consumption of infected bird carcasses when wild birds have died from avian influenza H5N1. Experimental research has also shown that ferrets and other mustelids are potentially susceptible to highly pathogenic avian influenza. However natural infections in carnivores appear to be self-limiting. Tuberculosis (Bovine TB) Pets can be exposed to TB from a variety of sources including infected cattle, badgers and other wildlife. Dogs and cats are variably susceptible to infection caused by Mycobacterium tuberculosis, M. bovis, M. microti and M. avium. Cats appear to have an innate resistance to M. tuberculosis. Tuberculosis has also been recorded in ferrets*. Clinical signs reflect the site of granuloma formation, but whether the infection remains at this site or disseminates systemically is determined by host immunity. Respiratory infection is more common in the dog, whereas the cat is more likely to develop cutaneous or intestinal disease. Granuloma formation in the lungs and mediastinal lymph nodes leads to cough, weight loss and pyrexia, while granuloma in the oropharynx may cause dysphagia, hypersalivation and retching. Generalized mycobacteriosis presents with splenomegaly, pleural or pericardial effusions, generalized lymphadenopathy, weight loss and fever*. A definitive diagnosis depends on demonstrating acid-fast bacilli. For classic tuberculosis the prognosis is grave. The decision to treat should be carefully considered in view of the zoonotic potential as well as the complexity and costs of treatment. Bovine TB is a zoonotic disease; therefore, where bTB in pets is disclosed, Animal Health or the private veterinary surgeon must inform the Consultant in Communicable Disease Control (CCDC) of the Local Health Authority so that any risks to human contacts can be investigated. If TB is reported in a farm cat or dog, the AHVLA will instigate TB testing of any cattle on the farm and other, potentially exposed cattle, on neighbouring premises. Anthrax Both dogs and cats are relatively resistant to infection with Bacillus anthracis. When it does occur it is usually through the ingestion of contaminated carcasses or animal by-products. Local inflammation of the upper gastrointestinal tract is followed by local and mesenteric lymphadenopathy. Diagnosis is made by the examination of Gram-stained blood smears or fine-needle aspirates, which show the characteristic Gram-positive rods. Aujeszky’s disease (pseudorabies) In dogs and cats pseudorabies usually presents as a per-acute rapidly fatal disease. Before death the animal may show ptyalism, pruritus, restlessness and aimless wandering, as well as depression. The disease is usually contracted through the ingestion of contaminated meat or offal. Brucellosis Brucella canis is prevalent in many areas of the world although it is believed to be absent from the UK*. Infected bitches may suffer abortion, most commonly between days 45 and 55 of pregnancy, although early resorption or stillborn puppies can also occur. In male dogs Brucella spp. may cause granulomatous epididymitis and prostatitis. B. canis can also affect other tissues, such as the eye (recurrent anterior uveitis) and skin (nodular and diffuse pyogranulomatous dermatitis), as well as being implicated in disco-spondylitis*. Serology for brucellosis should be undertaken in dogs that have been imported into the UK or in areas where Brucella canis is endemic; serological titres of 1:200 or greater are diagnostic for the disease. The isolation of the bacterium from blood or aborted tissues is diagnostic but as there are prolonged periods when a bitch is not bacteraemic, negative blood cultures do not rule out disease. The most common route of infection is venereal. ■ *For a useful list of links and references see the Advice section of www.bsava.com. companion | 11
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Companion May 2012 - BSAVA

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