Introduction

Zoonotic diseases have always been important. However, they are even more important now as the number of emerging diseases with zoonotic implications is increasing rapidly. Veterinarians have a large role to play in controlling these diseases and in advising their medical colleagues on the real risks that animal diseases pose to man. Zoonotic diseases can be viral, bacterial, fungal, protozoal and parasitic in origin. Veterinarians are uniquely qualified to advise on prevention and reduce the chances of transmission to humans by proper education and management techniques. Veterinarians have a duty of care to the general populace, to the owners of the animals concerned, to their own staff and of course to themselves. Washable protective clothing should be worn if possible.

There are some very simple measures which can be taken to protect yourself, your family and your staff from zoonotic diseases. You can also advise your clients how to protect themselves and their families as well as visitors to their farms:

• Never eat undercooked pig meat.

• Never cuddle newly born piglets or give mouth-to-mouth resuscitation.

• Always wash your hands thoroughly after handling pigs.

• Always wash your hands before handling food.

• Remove dirty clothes before entering the kitchen.

• Pay particular attention to the hygiene of children.

• Keep the farm clean.

• Keep pigs, their feed and water clean.

• Handle dung, manure, slurry and sewage safely.

• Protect water supplies and watercourses.

• Reduce transport stress of animals.

• Keep transport vehicles clean.

Viral Zoonotic Diseases Found in Pigs Categorized by Their Human Medical Name

Crimean–Congo haemorrhagic fever

This is a systemic disease affecting the blood vessels caused by a nairovirus and spread by ticks. It is found in pigs as well as in cattle, sheep and goats in Central Asia, Bulgaria and the Congo.

Encephalomyocarditis

Foot and mouth disease

FMD is a benign disease in man caused by an aphthovirus. It is the most contagious disease found in cattle, sheep, goats, South American camelids (SACs) and pigs known to veterinary science. There are rigorous control measures in place for its control. The disease has a rare incidence nowadays. Even in widespread pandemics in the past, cases seen in man were extremely rare. Man potentially can harbour the virus in the upper airway for 3 days after contact.

Influenza

This is a well-known generalized systemic disease caused by a variety of influenza viruses that is sometimes called grippe. It occurs in man worldwide. It is also found worldwide in pigs. Normally pig viruses are not infective to man. However, on occasions there are mutations so that pigs living in close contact to man will infect their keepers. On account of air travel such viruses soon occur in other countries. The human vaccines are regularly updated.

Japanese B encephalitis

This is a severe neurological disease caused by a flavivirus, which is spread in man by mosquitoes. It is found in pigs in India and the Far East. There is cross-infection between pigs and man by mosquitoes but this is rare.

Rabies

This a fatal neurological disease caused by a lyssavirus. It causes acute encephalitis both in man and animals and the pig is no exception. It is usually transmitted to humans by a bite from a carnivore. However, pigs can also transmit the disease by biting not only other pigs but in-contact humans. It is almost invariably fatal in man if post-exposure prophylaxis is not administered before the onset of severe symptoms.

The condition has been known for more than 4000 years. In the 4th century BC, Aristotle warned of the danger of being bitten by a rabid dog. In 1821, Francois Magendie, in France, showed that a dog would develop rabies if inoculated with saliva from a human case (Brightman, 2012). It was not until the 1880s that Louis Pasteur produced a successful vaccine.

The rabies virus is the most common rhabdovirus to infect man. It is readily destroyed by exposure to sunlight and by boiling. It is less easily destroyed by disinfectants. The virus is excreted in the saliva of infected pigs and other animals, including man. Excretion may occur 48 h before there are signs of the disease.

Rabies is found in most parts of the world except in the UK, Scandinavia, Australia and New Zealand. At least 100,000 people die each year from rabies, mostly in India and the Far East, in particular Thailand (Brightman, 2012). Rabies has been eliminated from domestic animals in countries such as the USA, so wild animals such as racoons are reservoirs of infection. In South America, vampire bats transmit rabies to pigs and sometimes to man.

Animals vary in their susceptibility to rabies. Wolves and foxes are very susceptible, whereas dogs are less so and wild boar and pigs even less so.

After a bite the virus enters the body and disappears rapidly from the site of inoculation, spreading to the brain by retrograde axoplasmic flow through the peripheral nerves. Once it has become established in the brain, it spreads back to the peripheral tissues through the nervous system. The incubation in pigs is similar to that in man. It is normally between 1 and 3 months, but a time of over a year has been recorded.

Diagnosis can be carried out in the live pig with a PCR on saliva, but more commonly the diagnosis is made by the finding of the pathognomic demonstration of Negri bodies in the cells of the hippocampus.

In very rare cases successful treatment has been carried out in man. Euthanasia should be carried out in pigs without damaging the brain, so that diagnosis can be confirmed.

Rotaviral gastroenteritis

There is a gastroenteric disease of children caused by a rotavirus. The virus found in suckling pigs worldwide is a different virus. However, if children receive a massive dose of the pig virus they will show diarrhoea. Normal hygiene procedures are important.

Swine influenza