Health Impact of Chikungunya and O’nyong-nyong in Senegal

Mosquito-borne viruses are a growing health concern around the world. Two of these viruses, chikungunya (CHIKV) and o’nyong-nyong (ONNV), can cause significant health problems. CHIKV was first found in Tanzania in 1952 and has led to big outbreaks in different places, including Africa, Asia, and the Americas. It mainly spreads through Aedes mosquitoes. The virus made headlines during a large outbreak in 2004 that started in Kenya and quickly spread to many areas, including the Indian Ocean islands and parts of Asia. By 2011, CHIKV reached the Western Hemisphere, and by 2014, thousands of people in the Caribbean and South America were infected.

ONNV was first found in Uganda in 1959 and has mainly caused outbreaks in East and West Africa. The first major outbreak happened between 1959 and 1962, impacting over 2 million people in these areas. A later outbreak took place from 1996 to 1997, mainly affecting Uganda, Kenya, and Tanzania. Even though ONNV is mostly found in Africa, cases have been seen in travelers coming back from areas where the virus is common.

People who get infected with CHIKV and ONNV generally recover on their own, but they can experience various symptoms such as fever, joint pain, rash, headache, and general discomfort. CHIKV is known for causing long-lasting joint pain in some individuals. Despite being largely confined to Africa, there is not much data about the health impact of ONNV because there is not enough monitoring. The symptoms of alphavirus infections are similar to those caused by other diseases, which makes it hard to diagnose accurately. This overlap in symptoms can lead to underreporting of cases, as many people might think they have another type of fever or illness.

In West Africa, including Senegal, CHIKV infections have been reported since 1960, with outbreaks continuing to occur up to 2023. However, we still do not have enough data on how common CHIKV and ONNV are in Senegal. This study aims to fill this gap by examining the levels of these viruses in Senegal and distinguishing between them using specific tests. By improving our understanding of how often these viruses are found, we hope to help public health efforts and offer insights into how mosquito-borne diseases spread in West Africa.

#Study Population and Ethics Statement

The samples used in this study were collected during efforts to monitor malaria and other non-malarial diseases among people living in Thies, Sindia, and Kedougou, Senegal. The samples from Thies and Sindia were part of efforts to track non-malarial febrile illnesses, while samples from Kedougou were collected to study malaria. All participants or their guardians provided informed consent for the collection and future use of their samples. The study followed ethical guidelines to ensure proper treatment of the subjects.

#CHIKV Testing Method

In this study, we used a specific test called an ELISA (Enzyme-Linked Immunosorbent Assay) to check for CHIKV virus-like particles in studied samples. This test involved coating special plates with the virus particles and then adding samples of blood serum to see if they reacted positively, indicating the presence of Antibodies against CHIKV.

#Microneutralization Tests

We performed microneutralization tests to check for antibodies in samples that were previously found to be positive for CHIKV. This involved diluting blood samples and mixing them with a known amount of CHIKV or ONNV. We then added these mixtures to special cells and examined them after a few days to see if the viruses had caused any damage. This test helps determine if the samples have protective antibodies against the viruses.

#Statistical Analysis

We collected information on the samples and analyzed it to understand the relationship between the presence of alphavirus antibodies and various factors like age, gender, and location. We used statistical software to conduct our analyses and create visuals to present the data comprehensively.

#Results of Testing

A total of 470 samples from non-sick individuals were examined in the study, collected from the three locations: Sindia, Thies, and Kedougou. Out of all samples tested for CHIKV antibodies, 117 were found positive, resulting in a general Prevalence of approximately 24.89%. The prevalence varied by location, with Sindia having 14.89%, Thies at 28.72%, and Kedougou showing a rate of 26.95%.

Further analysis indicated that participants over 40 years old were more likely to show exposure to CHIKV, and residents from Thies and Kedougou had higher chances of being exposed compared to other locations. A history of malaria was also linked to a higher chance of CHIKV exposure.

When we looked at ONNV, the prevalence of neutralizing antibodies varied greatly across locations. For CHIKV neutralizing antibodies, Sindia had a rate of 42.86%, Thies had 66.67%, and Kedougou had 14.47%. For ONNV, the rates were 28.57% in Sindia, 14.81% in Thies, and 50% in Kedougou. Notably, many individuals with CHIKV antibodies also showed responses against ONNV, showing a connection between the two viruses.

#Discussion of Findings

The results show important regional differences in the presence of CHIKV and ONNV in Senegal, indicating how local conditions can affect the spread of these viruses. The exposure rate to CHIKV and ONNV suggests these viruses are circulating more than previously acknowledged.

The analysis points to factors like location, age, and prior malaria history playing significant roles in determining a person’s risk of infection. The findings highlight the need for public health strategies focusing on these factors, especially with regard to mosquito control and monitoring efforts.

The high presence of neutralizing antibodies signifies ongoing circulation and potential for outbreaks. The differences between regions stress that local factors, including mosquito availability, can enhance transmission risks.

#Limitations of the Study

While this study provides valuable insights, it has some limitations. The data come from previous collections, which might not reflect the current situation accurately. There is also a lack of data on mosquito populations, which would help connect virus prevalence with mosquito activity. Additionally, our findings primarily indicate past exposure, not ongoing infections.

#Conclusion

The study reveals that CHIKV and ONNV are still active in Senegal, underscoring the need for continuous monitoring and preparation to handle these and other mosquito-borne viruses. The findings also highlight the crucial role of local conditions in shaping how these diseases spread. Overall, the study emphasizes the importance of combining vector control efforts with community health strategies to effectively manage the risks associated with these viruses. Future research should look into incorporating more comprehensive data to provide a better understanding of how these viruses behave and to help develop targeted approaches for intervention and prevention in affected areas.