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''Livestock are a major source, that's really important,'' Michael Maze, of Otago's Centre for International Health, said this week.
Leptospirosis is a major cause of febrile illness and death in Africa, and is transmitted from animals to people, but little is known about risk factors for human infection.
The disease affects more than 1million people worldwide each year, and causes about 59,000 deaths.
Dr Maze said the findings from two research papers, which have just been published in the scientific journal PLOS Neglected Tropical Diseases, had implications for potential control of leptospirosis in Africa.
The Otago-led studies amounted to a ''significant step forward'' and, given a ''finite resource'' of health funding, provided a clear indication the disease could be countered by improving health protection linked to cattle and rice-farming.
Dr Maze, who holds an MBChB from Otago University, has been based in Moshi, Tanzania.
He is a lead investigator in the studies, which involved research he undertook for his PhD thesis.
The studies are part of a larger collection investigating zoonotic infections in Tanzania that are led by Otago centre co-director Prof John Crump, and also involve Associate Prof Katrina Sharples of the Otago department of medicine, and overseas researchers.
The new research has shown that exposure to cattle and rice farming are risk factors for the disease in northern Tanzania, but that rodents, identified as related problems elsewhere, were not the main threat in this area.
In one study, the researchers tested rodents, cattle, goats and sheep for Leptospira infection and found cattle had a high prevalence of infection (7%), goats (1.2%) and sheep (1.1%).
Among 384 trapped rodents, no animals were found to carry the infection.
The researchers also investigated risk factors for the disease among 1293 patients with fever attending hospitals in northern Tanzania between 2012 and 2014.
The researchers identified work in rice fields as an important risk factor for human leptospirosis, where humans were infected through prolonged contact with water that may be contaminated by infected animal hosts.