Zoonoses

Hantavirus

Hantaviruses are a group of viruses that are normally carried by rodents, such as:

• rats
• mice
• voles

Each hantavirus is specific to a different rodent host. Once infected the rodent will secrete the virus for prolonged periods, probably for life.

Hantaviruses are almost exclusively transmitted through inhaling infectious aerosol from rodent excreta and fluids, such as:

• urine
• faeces
• contaminated bedding

The virus is also present in rodent saliva, so a bite is also a way of transmitting to humans.

The severity of the hantavirus infection varies from asymptomatic through mild to severe disease.

The hantavirus present in Europe, Asia and Africa tends to cause haemorrhagic and kidney disease, whilst new world hantavirus causes severe respiratory disease.

Hantaviruses cause two serious infections in humans:

• haemorrhagic fever with renal syndrome (HFRS)
• hantavirus pulmonary syndrome

Human behaviour plays a crucial role as a risk factor in the transmission of hantavirus infections. Preventing transmission is based on adopting personal preventive measures, such as avoidance of virus-contaminated dust through:

• cleaning with disinfectants
• improving ventilation
• wearing face masks

An information leaflet on reducing the risk of human infection from pet rodents can be found on the Public Health England website.

Toxocariasis

Toxocara canis is a roundworm parasite of dogs and foxes. The eggs of these parasites can survive in the environment for many years. Humans – usually children – can acquire Toxocara canis eggs by:

• ingesting soil
• direct contact with dogs – usually puppies
• consumption of uncooked or undercooked food contaminated with eggs

Some infections may be asymptomatic, but there are a number of clinical syndromes which are:

• visceral toxocariasis
• ocular toxocariasis
• covert toxocariasis

Visceral toxocariasis

Symptoms of visceral toxocariasis include:

• fever
• coughing and wheezing
• enlarged lymph nodes
• skin rash

Ocular toxocariasis

Ocular toxocariasis causes loss of visual acuity from blurring through to blindness, usually in only one eye.

Covert toxocariasis

Covert toxocariasis causes a milder form than visceral toxocariasis and ocular toxocariasis. Symptoms include:

• weakness and lethargy
• abdominal pain
• enlarged lymph nodes
• skin rash and hives
• headache
• coughing and wheezing
• limb pain
• nausea

More information on toxocariasis is available on the NHS website.

Trichinellosis

Trichinellosis is caused by roundworms of the genus Trichinella. Trichinellosis is caused by eating raw or undercooked pork and wild game products infected with the larvae of Trichinella spiralis. Infection can cause symptoms such as:

• diarrhoea
• abdominal cramps
• malaise

This can progress to fever, and in severe cases it can affect vital organs. The distribution is worldwide but trichinellosis is regularly found in:

• central and eastern Europe
• the Americas
• parts of Africa
• Asia