New Tanzanian study on the causes of livestock abortion can help address future mortalities and zoonotic diseases

Research approach addresses data gaps and provides local diagnostic training

A Tanzanian farmer living on the slopes of Mount Kilimanjaro bought a cow and her calf as an investment and a source of milk for his family, but as time went by, he realised there was a problem. The cow repeatedly suffered from stillbirths or was unable to carry pregnancies to term. As a result, she was not producing milk, which the farmer and his family relied on for nutrition and income. Disheartened, the farmer turned his attention to the calf when she was old enough to reproduce, but faced similar difficulties. That’s when a group of veterinary and animal health researchers stepped in. Tests revealed that both cattle were suffering from a chronic parasite infection which can reduce fertility and cause stillbirth, for which there is no treatment. Seeing that the cow and calf were unable to produce live offspring, the farmer decided to fatten them up and sell them at the local market for meat instead.

Livestock safeguard the livelihoods of pastoralist farmers, as providing a secure source of food, improving their wellbeing overall. With 50% of Tanzanian households dependent on livestock for their income, losing livestock and milk due to abortions – and often not knowing the causes – can be catastrophic. A new study is giving them answers and offers wider insights for Tanzania and beyond.

Investigating the causes of livestock abortion

Despite being one of the key causes of productivity losses, livestock abortion is not routinely investigated across the Global South. Some studies from high-income countries suggest that fewer than 35% of livestock abortions are attributed to specific diseases.

This leaves a research and knowledge gap on animal abortions in low-income countries, particularly in sub-Saharan Africa, and as a result, a lack of evidence for solutions. This is due to a combination of factors: lack of data collection at the national level, farmers’ restricted access to veterinary care, and limitations in diagnostic laboratory capacity. Many of the pathogens that cause livestock abortions are zoonotic, meaning they are transferrable from animals to humans. That means investigating the infectious causes of abortion is crucial not only to safeguard pastoralists’ livelihoods and the welfare of their livestock, but also for human health.

Livestock abortion as an early warning to humans

To address this data gap, a team of researchers undertook a study that combined field investigations and lab diagnoses to determine the causes of livestock abortion in Tanzania. The first-of-its-kind study collected samples from livestock abortion events from 71 cattle, 100 goats, and 44 sheep in three regions of northern Tanzania. The researchers found that 19.5% of abortion events were in fact caused by one or more of the infectious pathogens studied. Other causes can include physical trauma, poor nutrition and genetic abnormalities.

Investigating the causes of livestock abortion revealed important insights beyond simply providing data on how many abortions were caused by pathogens. In fact, detection of abortion in livestock can provide an early warning to humans that a pathogen exists in an environment, as many diseases triggering abortion in livestock are zoonoses. For example, the Tanzanian study also detected an outbreak of Rift Valley fever (RVF) in cattle. This triggered a retrospective review of patients at local hospitals with a fever and uncovered human cases of RVF which had previously gone undetected.

The researchers passed on the results to farmers as quickly as possible. The field team arrived at the abortion site within 72 hours and the laboratory team were usually able to get results to the field team within one week. This proactive and swift response ensured quick results, which were then communicated to the farmers in local languages.

Diagnostic training at the local and national level

The study has contributed positively to the welfare of farmers in the region. They were trained to recognise the symptoms of abortion to inform the livestock officers, and were updated on the results of laboratory tests so they could be well-informed prior to making decisions about their cattle.

Beyond the farmer level, the data has also been impactful at a national level. The study has provided crucial information to the Ministry of Livestock and Fisheries to help them prioritise disease interventions, as well as encourage training opportunities for diagnostic work in local laboratories.

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Designed to operate in countries with limited resources – such as where veterinarians may be scarce – the study and its approach could serve as a template for other countries. This could in turn help more farmers minimise their losses and allow them to be more involved in decisions about their livestock. For example, whether they should be treated, bred or sold, or simply just have a better understanding of the causes of abortion.

However, for this model to be successfully replicated beyond Tanzania, it requires adequate infrastructural investment and support for local veterinary services to collect, transport and test samples, as well as robust participation from local communities and networks. Many subsistence livestock farmers have little day-to-day access to basic veterinary care for their animals, which is an important limiting factor in sustainable development for these communities.

Easing pressure on the livestock sector

As African nations need to support a growing population, the livestock sector will continue to play a crucial role in helping them to keep up with demand for nutritious food, and to secure sufficient incomes for farmers and pastoralist people.  As safeguarding human and animal health is an important component of the Sustainable Development Goals, increasing surveillance efforts to diagnose the infectious causes of livestock abortion will ensure countries are better prepared to handle zoonotic diseases. Ultimately, this helps livestock farmers make smarter, more informed decisions about their cattle, protecting their income, health and well-being.
 

Further reading

• Thomas, K.M., Kibona, T., Claxton, J.R. et al. Prospective cohort study reveals unexpected aetiologies of livestock abortion in northern Tanzania. Sci Rep 12, 11669 (2022). https://doi.org/10.1038/s41598-022-15517-8
• de Glanville W.A., Allan K.J., Nyarobi J.M., et al. An outbreak of Rift Valley fever among peri-urban dairy cattle in northern Tanzania. Transactions of The Royal Society of Tropical Medicine and Hygiene, trac076, https://doi.org/10.1093/trstmh/trac076
• Explore One Health resources on livestockdata.org

This study was conducted by researchers at the University of Glasgow, the Nelson Mandela African Institution of Science and Technology (NM-AIST),Washington State University, Kilimanjaro Clinical Research Institute, Kilimanjaro Christian Medical University College, Moredun Research Institute, Tanzania Ministry of Livestock and Fisheries, and Edinburgh Napier University, and the University of Otagao, with funding from SEBI-Livestock.

Header photo: Pastoralists in Northern Tanzania move their goats across the landscape. A new study examines the cause of pregnancy loss in ruminants. Photo: University of Glasgow.