Leptospirosis - a work health safety issue

In the past wet season a significant number of NT stock workers have been affected by Leptospira Pomona.  Confirmed cases of leptospirosis in humans are reported by the NT Department of Health Centre for Disease Control. Leptospirosis is a notifiable disease in humans, commonly referred to as ‘Lepto’, poses a serious threat to staff working on cattle stations, particularly in the flood plain and rural Darwin/Katherine regions. Leptospirosis is caused by a number of strains of the Leptospira bacteria, which have the ability to infect both animals and also cause serious disease in humans. Animals infected include cattle, pigs, sheep, goats, horses, dogs and rats in addition to native wildlife including kangaroos.

Leptospirosis is highly contagious because of the many ways it can be spread from animal to animal, or from animals to humans. The disease can be spread through urine, or at birth or abortion, resulting in the contamination of water, feed, pastures and soil. Once in the environment, the bacteria are able to infect animals and humans through damaged skin or the membranes lining the nose, eyes or mouth. Stock workers are most likely to contract the disease when working in cattle yards or abattoirs with infected cattle. Infection can result from both direct exposure to urine when handling or slaughtering cattle and working in yards where the water, mud, soil or vegetation have been infected. ‘Bang tailing’ and cleaning of water troughs are two key activities which can pose a risk to stockpersons. Handling the foetus of an aborted calf, or assisting with calving can be a further source of infection for humans. Recreational activities that may pose a risk include camping, bushwalking, gardening and hunting.

The clinical signs in cattle will vary depending upon the strain of the disease. In general, animal signs associated with leptospirosis include weak newborns, fever, infertility, mastitis, jaundice, depression and anorexia. Abortion ‘storms’ may also be seen in cows that are greater than five months pregnant. Abortions may occur weeks after initial symptoms, or even in the absence of symptoms.  These signs are rarely recognised in the NT.

Symptoms in humans have been found to occur within 10 days; however can range from 4 to 19 days. The length of illness varies, with people being sick for a few days, or as long as three weeks or more. Relapses are common however it is rare for person to person transmission to occur. Symptoms can include any of the following: