Zoonotic Infections

What microorganisms cause us harm?

TB or tuberculosis is well known to the farming community, as it is a routine animal husbandry issue with compulsory cattle testing. It is also a current medical issue as with international travel, a mobile work force and immunosuppressant drugs used for a number of conditions, we are seeing a resurgence of the disease. A cough and night sweats can be associated with pulmonary or lung TB. Early diagnosis and treatment can effect a cure so don’t hang around if you have these symptoms. The same symptoms can also be associated with other serious conditions.

Brucellosis may be more familiar as a condition causing abortion in cattle but it can be transmitted to humans and should be considered as a possibility when symptoms of lethargy and fluctuating fever present.

Farmers and vets are also aware that lambing time can present a risk to pregnant women. Two organisms in particular, toxoplasmosis and enzootic abortion pose a threat to the health of pregnant women and the developing foetus. Listeriosis can be transmitted from sheep and unpasteurised products to humans and damage the pregnancy.

The TB and Brucellosis testing programmes help reduce the number of herds with these conditions and hence reduce the human cross infection risk. Advice given to pregnant women to avoid lambing is also vital. The pasteurisation process is a valuable method for eliminating the risk of many infections being transmitted in dairy products. Medically vulnerable groups are safer consuming only pasteurised products.

Hand hygiene has an important role to play as animal excrements can carry a range of organisms which cause vomiting and diarrhoea in humans. Some of the conditions are self limiting and reasonably mild but others can be fatal especially to vulnerable individuals, older people, the young or those with other medical problems. Ecoli, salmonella and cryptosporidium are all significant infections which can be caught as a result of poor hand hygiene. Even pet excrement carries the risk of infections which can damage the eyes and developing human foetus.

Episodes of diarrhoea lasting more than 24 hours should be tested by sending a sample for analysis via your GP surgery. The source of some infections needs to be traced by public health officials in case wide spread food or water contamination has occurred or is at risk of occurring.

Weil’s disease or Leptospirosis is a serious and potentially fatal condition, which can be contracted from contaminated water. Historically we as medical students were taught that stagnant ponds or streams or ponds with poor flow that can be accessed by vermin pose the greatest threat as rat urine is heavily contaminated. A vet friend advised me recently that in fact dairy farmers are at particular risk. Cows urinating in a milking parlour because of the stand height pose a threat to the farmer as droplet spread to the eye can cause transmission. Jaundice, headache and fever are major features of this condition, which can progress with fatal consequences if not correctly managed at an early stage. Eating or drinking with contaminated hands is ill advised although open wounds can also allow infection in.

Cuts and puncture wounds to the skin can introduce the Tetanus or ‘lock-jaw’ organism to the body. To someone without vaccination cover this can be a life threatening condition. As well as Tetanus risk, soft tissue infection can itself lead to blood poisoning or septicaemia so it needs to be treated appropriately particularly in diabetics.

Skin Infections
Ring worm is a condition most farmers are familiar with. It is caused by a fungal organism which can be passed to humans either from contact with the animal host directly or from contact with gates or posts they have rubbed against. Fortunately creams and tablets are now available which can clear this up quickly in humans.

Orf, which primarily affects lambs and can cause mastitis in sheep is also transmissible to humans and giving a painful unsightly infection on the hands.

Precautions

• Be informed. Know what the infection risks are in any given environment
• Use appropriate gloves or other protective gear
• Don’t eat drink or smoke with contaminated hands or lips
• Promptly use copious clean water to wash skin wound and protect healing wounds from contamination
• Know your tetanus vaccination status
• Animal excrement is full of micro organisms many of which can cause serious illness especially to younger and older people, pregnant women and those who are medically compromised
• Aborted animal material may be heavily contaminated and be a major risk to pregnant women
• All antibiotics both for animal and human use should be used respectfully as inappropriate use leads to resistant organisms evolving and current treatments becoming ineffective
• As symptoms do not present immediately in all conditions think back over a few weeks and seek early medical advice early if unwell giving a full account of possible exposures

  • Page last updated:19 December 2012