MICROBE 2018 recap - Microbes that Know No Borders - Zoonoses and "One Health"

Welcome to Tanzania...land where most patients entering the hospital for fever are treated empirically for malaria and there is a poor clinical response to antimalarial drugs.

Why might patients have poor antimalarial response and high case fatality rates?

Dr. John Crump, University of Otago, New Zealand

Zoonosis and a Paradigm for 'One Health' in Africa

A look at the malaria profile for Tanzania, we see that there is malaria prevalence in the country ranging from 1-33%, with an average of about 10%. While it has been declining of recent there are 10-12 million cases annually with 60-80 thousand deaths per year.

So it stands to reason if a feverish individual walks into a hospital or clinic, many of which are limited in terms of tests and diagnostics that those individuals would be empirically diagnosed with malaria and given antimalarials. However, they are finding that there are poor responses to those antimalarial drugs and high case fatality rates.

It is most likely due to non-malaria-related infectious diseases. Enter Leptospirosis...one of those neglected tropical diseases.

• Maze, Michael J., et al. "Risk factors for human acute leptospirosis in northern Tanzania." PLoS neglected tropical diseases 12.6 (2018): e0006372.
• Allan, Kathryn J., et al. "Assessment of animal hosts of pathogenic Leptospira in northern Tanzania." PLoS neglected tropical diseases 12.6 (2018): e0006444.
• Dobigny, Gauthier, et al. "Leptospirosis and Extensive Urbanization in West Africa: A Neglected and Underestimated Threat?." Urban Science 2.2 (2018): 29.
• Zain, Siti Nursheena Mohd, and Maria-Gloria Basáñez. "Collaborate or Collapse: Capacity Building in Zoonotic and Neglected Tropical Disease Modelling." Trends in Parasitology(2018).
• Pakoa, Junior George, et al. "High incidence of leptospirosis in an observational study of hospital outpatients in Vanuatu highlights the need for improved awareness and diagnostic capacities." PLoS neglected tropical diseases 12.6 (2018): e0006564.

Leptospirosis:

• Zoonotic pathogen with multiple hosts - humans, mice, agricultural animals, wild animals, birds all via the environment
• Your immune response can eliminate the infection but it can still persist
• There is an overlap of symptoms which makes diagnosis challenging and costly.
• Rodents in slums or rice paddies are traditionally singled out as the culprits but much of the research pointing the figure is out of SE Asia rather than Africa.

So what's going on in Africa?

• The predominant serogroup is dominated by L. australis which is found in cattle, dogs, rats, sheep, pigs, donkeys, hedgehogs!...Well gee...that narrows it down?!
• When a risk factor analysis was conducted, risk factors for Leptospirosis included:
• cattle waste
• fed cattle
• farmer
• working in a rice field
• But rats were NOT found to be associated with an increased risk for leptospirosis infection...but this is difficult to measure
• qPCR analysis eventually determined that there was a high prevalence of Leptospira in cattle! They also assay rats and sheep - no rates, and only 3 sheep came up positive.



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• They also found an overlap between serogroups found in humans and cattle including in the L. australis strains.
• Exposure to rice fields was also associated with a higher risk for leptospirosis but in Africa the probability of coming across a rice paddy/field ...it's safe to say that's pretty minimal.

So it looks like the main source of leptospirosis infection in Tanzania is through exposure to cattle with an increase in risk with large mixed herds.

Combating this would include outreach and education, livestock interventions and cost effective analysis workflows so that risk can be continually assessed during interventions.