FAQs Leptospirosis

Questions

General

1. Is Leptospirosis a greater problem in New Zealand than elsewhere in the world?   Answer
2. WHY is NZ top of the list?  Answer
3. What's the risk for me?   Answer
4. Can people be vaccinated?  Answer
5. Can humans be protected by vaccinating animals?  Answer
6. Is meat quality affected by Leptospira infection?  Answer

Answers

General

1. Is Leptospirosis a greater problem in New Zealand than elsewhere in the world?
    Answer: Not really - the risk is presumed to be much higher in tropical countries such as many of the Pacific Islands (e.g. New Caledonia, Fiji, Samoa), South and South-East Asia (e.g. India, SriLanka, Bangladesh, Phillipines) or South America (e.g. Ecuador, Brazil). However, NZ holds the first position among temperate climate countries of the OECD ('industrialized' or so called 'developed' countries) in terms of the annual incidence of notified human cases of severe illness.
   
   
2. WHY is NZ top of the list?
   Answer: we don't have the final clue - there are two major plausible factors, (i) the mild climate of having winters without frost in most parts of the country, hence soil does not freeze allowing bacteria to survive for extended periods, and (ii) the way that domestic livestock are kept on pasture for 12 months with permanent access to urine-contaminated water and soil. The latter two reasons would explain the high endemic level of prevalent shedders among sheep flocks, beef cattle herds, most likely wild animals (possums, rabbits, hedgehogs ectc.), and possibly even dairy cows despite vaccination. Consequently, people in frequent and close contact with live animals or carcasses at slaughter (esp. home slaughter!) have a higher risk of getting infected than elsewhere.
   
   
3. What's the risk for me? 
   Answer: this of course depends on the intensity of contact with animals. research found approximately 5% veterinarians and farmers and 5-20% (depending on species slaughtered) abattoir workers to have evidence of contact with Leptospira. Recent data from abattoir workers demonstrated that 80% infections remained silent (no signs of disease) and 20% showing mild or severe clinical signs such as head and limb aches, and general debility. As an example, the risk of illness due to Leptospirosis among workers at sheep abattoirs was 2.7% for each year of work, that is 2-3 per 100 workers would get ill with this disease during a course of 12 months. The risk for farmers is likely much lower as they have less intensive and less frequent contact with animals. It may half as high or less, based on the prevalence of antibody found in meat workers versus farmers or vets.
   
   
4. Can people be vaccinated?
   Answer: Yes and No - yes, because there is evidence from several countries about vaccines and vaccine efficacy. Trials in Cuba showed about 50% vaccine efficacy. A vaccine is commercially available in France to specifically protect sewer workers against infection with a single serovar ('icterohaemorrhagiae'). No, because we do not have a vaccine that is registered in AUS or NZ, probably because there are too many serovars to be included to achieve sufficient protection (50% may be to low to be acceptable) and the development and registration of a vaccine is a long and expensive process. Hence, no attempt is currently in sight for even starting such a challenging undertaking. In the absence of a vaccine for people, control therefore relies on vaccinating animals.
   
   
5. Can humans be protected by vaccinating animals?
   Answer: Yes if it is done right! A recent review of vaccine efficacy studies showed that commercial vaccines can be regarded as effective as long as vaccination precedes infection. After infection, the protective effect of vaccination is substantially reduced. Vaccination needs to target young replacement animals at about 1-3 months of age. they should have completed the schedule (2 shots within 4-6 weeks) by reaching 6 months of age, and a single booster vaccination should be provided once a year in 12 months intervals. In very high challenge situations, e.g. after floods or when outbreaks were observed, more frequent boosters may be advisable, e.g. every 6 months.
   
   
6. Is meat quality affected by Leptospira infection?
   Answer: No, there is currently no evidence that humans get infected with Leptospira from processing meat in the kitchen or consuming meat in any form. The principal 'survival' place for these bacteria is the kidney where they find a save haven in the interior of tubular cells, well away and protected from the reach of antbodies. They occasional 'see the light of day' when being excreted into urine. Thus, meat is probably rarely if ever contaminated with Leptospira, and if so in very small amounts. Moreover, infection occurs through contact of urine with wounds, skin abrasions, or the mucosa of eyes, mouth and nose - and this is unlikely to happen through contact with meat. Hence, Leptospirosis among domestic livestock is unlikely to ever become a public health concern of the meat industries.