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Q fever (QF) and Rift Valley fever (RVF) are endemic zoonotic diseases in African countries, causing significant health and economic burdens. Accurate prevalence estimates, crucial for disease control, rely on robust diagnostic tests. While enzyme-linked immunosorbent assays (ELISA) are not the gold standard, they offer rapid, cost-effective, and practical alternatives. However, varying results from different tests and laboratories can complicate comparing epidemiological studies. This study aimed to assess the agreement of test results for QF and RVF in humans and livestock across different laboratory conditions and, for humans, different types of diagnostic tests. We measured inter-laboratory agreement using concordance, Cohen's kappa, and prevalence and bias-adjusted kappa (PABAK) on 91 human and 102 livestock samples collected from rural regions in Chad. The serum aliquots were tested using ELISA in Chad, and indirect immunofluorescence assay (IFA) (for human QF and RVF) and ELISA (for livestock QF and RVF) in Switzerland and Germany. Additionally, we examined demographic factors influencing test agreement, including district, setting (village vs. camp), sex, age, and livestock species of the sampled individuals. The inter-laboratory agreement ranged from fair to moderate. For humans, QF concordance was 62.5%, Cohen's kappa was 0.31, RVF concordance was 81.1%, and Cohen's kappa was 0.52. For livestock, QF concordance was 92.3%, Cohen's kappa was 0.59, RVF concordance was 94.0%, and Cohen's kappa was 0.59. Multivariable analysis revealed that QF test agreement is significantly higher in younger humans and people living in villages compared to camps and tends to be higher in livestock from Danamadji compared to Yao, and in small ruminants compared to cattle. Additionally, RVF agreement was found to be higher in younger humans. Our findings emphasize the need to consider sample conditions, test performance, and influencing factors when conducting and interpreting epidemiological seroprevalence studies. Author summary: Q fever (QF) and Rift Valley fever (RVF) are zoonotic diseases that can be transmitted from animals to humans, causing health problems and economic losses in African countries. While various diagnostic tests for these diseases are available, they can be impractical, especially in resource-limited settings. For this study, human and livestock samples from Chad were first tested in a local laboratory using a routine test (enzyme-linked immunosorbent assay). Serum aliquots were then sent to laboratories in Germany or Switzerland for retesting, using the same test type for livestock and a different test type for human samples. We analysed the agreement between the test results and investigated the influence of the demographic characteristics of the sampled individual on this agreement. Our findings are crucial as they reveal discrepancies in test results, even though the samples originated from the same individuals. Additionally, we found that factors such as the age of the sampled individual influenced test agreement. This study underscores the importance of considering sample conditions, test performance, and influencing factors when conducting and interpreting disease prevalence studies. Enhancing diagnostic procedures will aid in more effective disease control management, benefiting local communities and global health efforts. [ABSTRACT FROM AUTHOR]

Introduction: Tuberculosis (TB) is an infectious zoonotic disease caused by bacteria belonging to the Mycobacterium tuberculosis complex. In sub-Saharan African countries such as Chad, TB is endemic and causes a high burden on humans and animals through morbidity, mortality, and reduced productivity in livestock. To effectively prevent and control the disease, strong coordination between policymakers, health and veterinary services, civil society organizations, and communities is needed. It also requires an understanding of the knowledge the communities have regarding TB. However, such knowledge is under-investigated, especially in rural areas. How knowledge affects people's attitudes and practices is also unclear. The main objective of this study was to investigate the knowledge, attitudes, and practices (KAP) of Chadian rural communities to better involve them in TB surveillance programs. Methods: A survey was conducted in 2021 in five rural health centers. Face-to-face interviews were conducted with persons suspected of having TB, and data on KAP were recorded and analyzed. Results: In total, 139 participants were enrolled. Overall, the knowledge and attitude of the participants were found to be good tomoderate, with 126 (90.6%) and 97 (69.7%) having good knowledge and attitude, respectively. However, their practices were found to be rather weak, with only 40 (28.7%) participants having good practices. Men were found to have good knowledge about the disease significantly more often than women. Poor attitude was significantly associated with a mobile lifestyle compared to settled lifestyles and with farmers (mainly engaged in agriculture) compared to breeders (livestock keepers). Poor health practices were associatedmore withmen than women and with settled lifestyles compared to amobile lifestyle. Good practices were found to be in line with good knowledge and good attitudes; however, in the analyses, the association was not significant [OR knowledge = 5.83 (95% C.I. 0.6842.83), p = 0.112; OR attitude = 2.09 (95% C.I. 0.875.04), p = 0.100]. Furthermore, attitude was not associated with knowledge [OR = 1.03 (95% C.I. 0.303.55), p = 0.964]. Discussion and conclusion: Our study highlights the need for targeted sensitization and awareness campaigns for communities with poor knowledge and attitudes regarding TB. These campaigns should also include practical training to increase the level of good practice rather than simply providing knowledge. [ABSTRACT FROM AUTHOR]

Background. Since the start of the COVID-19 pandemic, Chad has had 7,417 confirmed cases and 193 deaths, one of the lowest in Africa. Objective. This study assessed SARS-CoV-2 immunity in N'Djamena. Methods. In August-October 2021, eleven N'Djamena hospitals collected outpatient data and samples. IgG antibodies against SARSCoV-2 nucleocapsid protein were identified using ELISA. "Bambino Gesù" Laboratory, Rome, Italy, performed external quality control with chemiluminescence assay. Results. 25-34-year-old (35.2%) made up the largest age group at 31.9±12.6 years. 56.4% were women, 1.3 women/men. The 7th district had 22.5% and the 1st 22.3%. Housewives and students dominated. Overall seroprevalence was 69.5% (95% CI: 67.7-71.3), females 68.2% (65.8-70.5) and males 71.2% (68.6-73.8). >44-year-old had 73.9% seroprevalence. Under-15s were 57.4% positive. Housewives (70.9%), civil servants (71.5%), and health workers (9.7%) had the highest antibody positivity. N'Djamena's 9th district had 73.1% optimism and the 3rd district had 52.5%. Seroprevalences were highest at Good Samaritan Hospital (75.4%) and National General Referral Hospital (74.7%). Conclusion. Our findings indicate a high circulation of SARSCoV-2 in N'Djamena, despite low mortality and morbidity after the first two COVID-19 pandemic waves. This high seroprevalence must be considered in Chad's vaccine policy. [ABSTRACT FROM AUTHOR]

Zika virus (ZIKV) is a major public health problem worldwide. After several reported outbreaks, the current extent of infections caused by this orthoflavivirus in the Sahel remains to be explored. We investigated the prevalence of neutralizing antibodies against ZIKV in the general population, in HIV-infected individuals and in livestock in Chad using a seroneutralization assay that ensures high specificity level. In this retrospective serological serosurveillance investigation, we estimated the neutralizing seroprevalence to be approximately 26% (18/69) in healthy Chadian participants and 17% (16/94) in HIV-infected individuals, with no statistical difference between these two subgroups or genders. In addition, we found an overall ZIKV prevalence of 14% (8/59) in small ruminants (sheep and goats) living in the Lake Chad Basin area, demonstrating virus circulation in animals. Our pilot study shows for the first-time evidence of ZIKV circulation in humans and in livestock in Chad in close interaction with humans, and highlights the main challenges associated with this virus in Sahelian areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The seroprevalence of Rift Valley fever (RVF), brucellosis, and Q fever among domestic ruminants on the southeastern shore of Lake Chad was studied. The study area consisted of two parts, including mainland and islands. On the mainland, the study was conducted in nine randomly selected villages and camps. On the islands, samples were collected from all four available sites. A total of 985 serum samples were collected and 924 were analyzed using enzyme-linked immunosorbent assay (ELISA) for RVF. A total of 561 samples collected from islands were analyzed using ELISA for Q fever and both ELISA and Rose Bengal tests (RBT) for brucellosis. The apparent RVF seroprevalence by species was 37.8% (95% confidence interval [CI] 34.2-41.3) in cattle, 18.8% (95% CI 12.3-25.2) in goats, and 10.8% (95% CI 3.0-18.5) in sheep. For brucellosis and Q fever, only cattle samples from islands were analyzed. For Q fever, the apparent seroprevalence was 7.8% (95% CI 5.6-10.1). For brucellosis, the RBT showed a prevalence of 5.7% (95% CI 3.8-7.6), and ELISA showed 11.9% (95% CI 9.3-14.6) with a kappa value of 0.53 showing a moderate agreement between the two tests. This study confirms the presence of the three diseases in the study area. More research is required to assess the importance for public health and conservation of the Kouri cattle breed.