Tropical Health Matters

Anthony AHUMIBE is a staff member of Nigeria CDC and presently a doctoral student at the Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan. Herein he examines the challenges posed by Lassa Fever to the West African region.

Following the West Africa Ebola epidemic of 2014, the global community has been preoccupied with Lassa fever, a zoonotic viral infection that has caused sickness and death in some communities in Nigeria, Liberia, Sierra Leone, and Guinea. Familiar challenges like absence of vaccine and point of care diagnostics are being handled through investments in research and development. There are, however, some imperceptible yet weighty challenges along the path of Lassa fever control.

The recent finding by Happi and colleagues shows that several species of household rodents, nonspecific to the familiar multimammate rats and other peri-urban small animals carry the Lassa virus and demonstrate that the virus is adapting. Conversely the economic turn of events in the endemic countries indicates that more people are moving into poverty and are unable to make proper hygiene choices. Furthermore, the expansion of city slums, and poor structured housing increases the opportunity for human contact with these rodents, thereby increasing rodents to human virus transmission.

The table derives from weekly reports published by NCDC. Nigeria Lassa fever data summary for Epi week 15, 2024 is compared with Epi Week 15 cumulative data in 2023 and 2024 (Courtesy: Nigeria CDC Situation report).

Related to the issue of homestead hygiene is the ineffective management of hospital waste in most of these communities. Many cases of Lassa fever slip through the cracks as malaria fever in health centres with limited capacity for molecular diagnosis.  After treatment, body fluid-stained dressings and disposables as well as serum and other body fluids are disposed as waste. The ineffectual medical waste management, so unsupervised, promotes fomite-rodent transmission and genetic spill-over to other species of household animals.

Citizens in the endemic countries share the same burden of poor health infrastructure and limited access to healthcare. For instance, only about 3% of adults aged 15-49 years have a form of health insurance. The high out-of-pocket expenditure required has caused increased hesitance in visiting hospital. As an alternative, many persons become victims of charlatans while genuine traditional healers who approach medical care blindly and without protective equipment become targets of infection and sources of transmission.

The photo (by author) shows the traditional sun drying of grated cassava for fufu meal. This exposure increases potential for Lassa fever transmission through contamination with rodent excreta.

The large trust deficit between the citizens and the political leaders owing to the several years of perceived economic and social mismanagement is also a great source of concern. Trust in the system by the people has been affirmed as necessary in advancing the cause of public health. Marcia McNutt and Michael Crow wrote in their op-ed, published in Issues in Science and Technology magazine that scientists and elected leaders need to earn citizens’ trust to win the war against misinformation and disinformation. Hesitancy in uptake of available countermeasures, appropriate risk perception and required behavioural change, seem imperiled in these communities due to the lack of trust in government and government institutions.

Finally, it is often assumed that every new infection cycle is initiated by human contact with rodent or rodent fluid. This does not consider however that the reinfection cycle could have started from a lab leak. Pathogen escape pathways are preponderant with many vials of remnant serum held unaccounted for in many public and private care institutions, some in community hospitals. This can only change if these countries develop a national system for accountability and repository of high-consequence pathogens.

The 2024 World Malaria Day Theme of “Gender, Health Equity, and Human Rights” cannot be divorced from the inequities of climate change wherein the countries that contribute the least to the problem suffer the most, including the deleterious effects of changing malaria geographics. The current severe drought in Zambia, Zimbabwe, and Malawi is a case in point.

As a recent headline in VOA news states, “UN officials in Zambia to assess worst drought in 20 years.” The government has declared a drought officially where it “has affected a total of 8 provinces across the country with highest impacts in Southern, Central, Eastern, North-western, Western, and Lusaka Provinces.”

Drought should not be confused with a “normal” dry season. What we are seeing in Southern Africa now is an extended dry period in what should have been the rainy season. A study in Mali suggests that adult malaria-carrying mosquitoes “have endured the dry season by aestivating—the hot-weather equivalent of hibernating.” Unfortunately, an extended dry period of a drought may be more difficult to endure for the adults, but possibly the eggs are more resistant. Additional studies paint a more complicated picture.

Weather cycles intensify with climate change. El Niño, which can lead to droughts also produces warming in higher elevations so there tends to be an increase in malaria transmission in areas in the highlands.

Research in Zambia published just two years ago reported increasing trends of malaria in areas covering over 47% of all health facilities, while a declining trend was seen in areas covering 27% of health facilities. The decreasing trend was noticeable in the south, where malaria risk is lowest, and current drought conditions higher. The authors stress the need for continued geographic surveillance and implementation of control strategies geared to the conditions in each area.

A systematic review of the effects of climate change identified “vector borne disease (including malaria, dengue and West Nile Virus)” as a major concern as well as “nutrition-related effects (including general malnutrition and mortality, micronutrient malnutrition, and anti-nutrient consumption),” which compromises the ability of children to fight disease. The review found different impacts of drought ranging from increase mortality a year after a drought, to the disappearance of some vector species. The lesson is that each country needs to monitor their situation carefully. For Zambia, UNICEF reports that, “significant number are children, at risk of food insecurity, acute malnutrition, and disease.”

Research on drought effects on malaria arose from a study that examined the effects of drought on malaria infection (genetic) complexity and transmission in lizards (Plasmodium mexicanum and Sceloporus occidentalis). The authors noted that, “relationship between rainfall and parasite prevalence is somewhat more ambiguous.” Thus, the authors recommended that more information is needed about human malaria parasites and drought since “drought may cause shifts in human disease outcomes independent of any changes to prevalence.”

The United Nations challenges us by observing that, “Due to the complex relationship between malaria and climate change, gaps in knowledge still exist in the mechanisms of the linkage.” Changes in temperature, rainfall, and humidity need to be monitored for effects on vectors, parasites, and human movement. The current situation requires a more nuanced and complex approach to interventions if malaria elimination can be achieved while also preventing gender discrimination, promoting health equity and preserving human rights.