Reflections on the role of One Health in Lassa Fever diagnosis, case management, and innovation

Every year, Lassa fever, a zoonotic disease of major public health concern in many West African countries, including Nigeria, Benin, Guinea, Liberia, Sierra Leone, makes at least 300,000 people sick and kills at least 5000. Yet not rapid diagnostic or effective therapeutic or vaccine exists.

Despite increased research in recent years, we still do not fully understand the dynamics of the Lassa virus. Gaps include a lack of detailed understanding of the viral and host immune factors in the virus life cycle, activation and suppression of host innate and cellular immunity against the virus and implications for disease progression, and animal models required for vaccine and therapeutic testing. Answering such questions can help build a road map for the development of effective vaccines and therapeutics for this deadly disease.

As a laboratory scientist in the Kenema Government Hospital (KGH) Viral Hemorrhagic Fever  Laboratory (VHF Lab) in Sierra Leone and an MSc candidate at the London School of Hygiene and Tropical Medicine, I am engaged in a diverse set of work as part of ongoing research efforts as well as supporting routine diagnosis of clinical samples to inform case management. The VHF lab confirmed the first infection with Ebola Zaire virus during the Ebola outbreak in 2013-2014., The VHF Lab also performed metagenomics sequencing for the first set of positive SARS-CoV samples collected in-country, helping to inform about circulating strains and transmission dynamics. Currently, we are engaged in several studies with different research partners, including with LEAP4WA, where we are conducting observational research and are in preparatory stages for interventional studies.

The mortality rate due to Lassa fever is relatively high. But with no approved vaccines or targeted therapeutics, case management depends on supportive care, with ribavirin the therapeutic of choice. Effective and timely diagnosis thus plays a crucial role. Yet, many people who fall ill and die from Lassa fever live far from diagnostic laboratories. Considerable delays between when samples are collected and arrive at the lab for testing can have great impact on both diagnosis and case management. Simply put, the longer someone has to wait for a diagnosis, the more time the virus has to proliferate and for the disease to take hold.

It’s crucial we develop safer and easy-to-use bedside diagnostic kits, like rapid diagnostic tests, which should be available in all primary healthcare facilities, no matter how far from the main laboratory. In doing so, anyone with symptoms of Lassa fever will be tested and if positive, samples can be sent to the main laboratory and the patient quickly referred to the appropriate healthcare facility, increasing the chances of early diagnosis, treatment, and survival. We must also increase awareness of Lassa fever, which remains low among healthcare providers in some areas. Many doctors, for example, first suspect other diseases and may rule out Lassa fever until symptoms worsen and the appropriate diagnostics are requested.

Taking a more global view, One Heath offers a key approach to respond to zoonotic diseases. Any preventive approach must also target the animal vector; in the case of Lassa fever, the Natal multimammate mouse [Vora et al. 2023; Klitting et al. 2022; Rabinowitz & Conti 2013]. One such approach is to use pest control measures, such as using pesticides around homes or biological controls such cats to feed on and deter rodents. Genomic surveillance offers a more contemporary approach. It was through the power of genomics that scientists first identified that the virus spread from the multimammate mouse to humans, and then from human to human. This work continues to inform Lassa fever science today. For example, by testing animals in the field, researchers can detect viral reservoirs in the animal host early and inform authorities to take prompt action, potentially even breaking the chain of transmission. Then, if there is an outbreak, researchers collect samples from close contacts, generating data to map the chain of transmission, and build a more accurate picture of the outbreak to inform a more effective outbreak response.

As a deadly zoonotic disease with no approved vaccine or therapeutic, a One Health approach that considers the many different angles of Lassa fever is crucial to better understand the dynamics of viral spread and infection between the animal host and humans. Multiple new tools are urgently needed as part of this response. Novel and easy-to-use diagnostics that can even be self-administered at home are just one part of the puzzle. The development of an affordable and effective Lassa fever vaccine remains a key priority of the scientific and public health communities. I’m proud to be contributing to these complementary efforts through my work with KGH and LEAP4WA.