We often take children to farms so they can experience animals at close hand. By and large, this is of no consequence, as long as strict hygiene conditions are adhered to. Of course, it is incredibly difficult to guarantee that a child will follow even the simplest of hand-washing protocols.
A vast number of clinical conditions - called zoonoses - may be contracted from animals. A range of animals, from sheep, goats and cattle to more exotic creatures, may pose concern.
Humans may develop zoonoses through a number of different routes, most commonly by ingesting bacteria or viruses after coming into contact with animals or animal faeces. In addition, disease may be acquired through broken skin, including bites or scratches, or through the lungs or even the eyes. Insects may also transmit infection from animals to humans.
CLINICAL CONDITIONS
E. Coli is perhaps the most commonly talked about zoonosis. This is a serious bacterial infection that often occurs in outbreaks. E. Coli infection can cause bloody diarrhoea and kidney failure. In most instances, the bacteria are harmless to the host animals, but it only takes a few bacteria to cause serious harm in humans. The condition has a high mortality rate. Salmonella and campylobacter may also be contracted from animals, causing diarrhoea.
Q Fever is caused by a species of bacteria called Coxiella burnetti. It may be acquired from inhaling dust that has been contaminated by animal faeces or urine, skin abrasions or even tick bites. Drinking unpasteurised milk can also lead to Q fever. The main culprits are sheep and cattle. Those with Q fever develop a flu-like illness but in some cases, pneumonia may ensue. Susceptible people may develop liver or even heart damage.
Lyme disease is a tick-transmitted zoonosis caused by the bacteria borrelia burgdorferi and is seen in forest areas such as the New Forest. Apart from the classic sign of a rash, Lyme disease is also associated with nerve damage, arthritis and heart involvement.
Leptospirosis is a bacterial infection commonly acquired through exposure to animal urine. There were 74 cases reported in England and Wales in 2007. The condition may not cause any symptoms at all; or, at its worst, infection may cause Weil's disease leading to hepatitis and jaundice, kidney failure, meningitis or even death.
Psittacosis, pronounced sit-ak-osis, is a bacterial infection associated with poultry. Inhalation of dust or aerosolised animal faeces or animal nasal discharge may transmit the bacteria.
Like Q fever, psittacosis may cause a flu-like illness in the early stages of the disease. Subsequent complications may be serious and include pneumonia, hepatitis, infection of the heart known as endocarditis, or even death.
Cryptosporidiosis is a parasite that can cause mild to severe watery diarrhoea, fever and abdominal pain. Around 4,000 cases are notified to the Health Protection Agency annually. Children aged one to five are particularly susceptible. Ingesting soil or water contaminated with infected animal or even human faeces is the normal route of infection.
Toxocara is a roundworm infection and is particularly common in dogs. Toxocara eggs are found in the faeces which contaminate soil. The eggs are sticky and may adhere to fingers, toys, foods and so on. A child may not show any symptoms after ingestion of the egg, although, at its worse, toxocara can affect a number of organs, including the lungs, liver, spleen and brain. If the eyes are involved it may cause blindness. Worming animals and teaching everyone effective handwashing will help to reduce the effects of toxocara, as would better education about the risks, and appropriate environmental legislation.
Toxoplasmosis is caused by a parasitic infection known as toxoplasma gondii and is often associated with cat faeces, undercooked meat or under-pasteurised goat's milk. Most infections do not cause symptoms, although one in ten infected people may experience a flu-like illness. The main concern is maternal infection during pregnancy that may cause a condition called 'congenital toxoplasmosis' in the unborn child, putting the woman at high risk of miscarriage. Problems associated with congenital toxoplasmosis in children who survive include brain damage, deafness, blindness and problems with growth.
Ringworm is a skin infection caused by a fungus. Animal carriers include cattle, pigs, sheep, horses and domestic pets. The fungus causes inflamed, crusty skin lesions.
Orf is another skin zoonosis, caused by a parapox virus. The main source is sheep and goats. Orf causes painful blisters which tend not to be serious. Bacteria may infect the blisters, requiring antibiotics.
PREVENTION
Each of the many zoonoses are complex; many are mild but some are potentially devastating. Identifying the infection and treating it early can limit the damage it may cause. But the most important strategy in combating zoonoses is prevention. Careful hygiene and child supervision, robust environmental laws and policing, as well as responsible animal ownership, are required to reduce the risk of transmission of disease to children.
Dr Raj Thakkar BSc(Hons) MBBS MRCGP MRCP(UK) is a full-time GP in Buckinghamshire