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Free roaming domestic dogs (FRDD) are the main vectors for rabies transmission to humans worldwide. To eradicate rabies from a dog population, current recommendations focus on random vaccination with at least 70% coverage. Studies suggest that targeting high-risk subpopulations could reduce the required vaccination coverage, and increase the likelihood of success of elimination campaigns. The centrality of a dog in a contact network can be used as a measure of its potential contribution to disease transmission. Our objectives were to investigate social networks of FRDD in eleven study sites in Chad, Guatemala, Indonesia and Uganda, and to identify characteristics of dogs, and their owners, associated with their centrality in the networks. In all study sites, networks had small-world properties and right-skewed degree distributions, suggesting that vaccinating highly connected dogs would be more effective than random vaccination. Dogs were more connected in rural than urban settings, and the likelihood of contacts was negatively correlated with the distance between dogs’ households. While heterogeneity in dog's connectedness was observed in all networks, factors predicting centrality and likelihood of contacts varied across networks and countries. We therefore hypothesize that the investigated dog and owner characteristics resulted in different contact patterns depending on the social, cultural and economic context. We suggest to invest into understanding of the sociocultural structures impacting dog ownership and thus driving dog ecology, a requirement to assess the potential of targeted vaccination in dog populations.

The apparent failure of global health security to prevent or prepare for the COVID-19 pandemic has highlighted the need for closer cooperation between human, animal (domestic and wildlife), and environmental health sectors. However, the many institutions, processes, regulatory frameworks, and legal instruments with direct and indirect roles in the global governance of One Health have led to a fragmented, global, multilateral health security architecture. We explore four challenges: first, the sectoral, professional, and institutional silos and tensions existing between human, animal, and environmental health; second, the challenge that the international legal system, state sovereignty, and existing legal instruments pose for the governance of One Health; third, the power dynamics and asymmetry in power between countries represented in multilateral institutions and their impact on priority setting; and finally, the current financing mechanisms that predominantly focus on response to crises, and the chronic underinvestment for epidemic and emergency prevention, mitigation, and preparedness activities. We illustrate the global and regional dimensions to these four challenges and how they relate to national needs and priorities through three case studies on compulsory licensing, the governance of water resources in the Lake Chad Basin, and the desert locust infestation in east Africa. Finally, we propose 12 recommendations for the global community to address these challenges. Despite its broad and holistic agenda, One Health continues to be dominated by human and domestic animal health experts. Substantial efforts should be made to address the social–ecological drivers of health emergencies including outbreaks of emerging, re-emerging, and endemic infectious diseases. These drivers include climate change, biodiversity loss, and land-use change, and therefore require effective and enforceable legislation, investment, capacity building, and integration of other sectors and professionals beyond health.

Only a minority of the patients with acute febrile jaundice evaluated through the Yellow Fever surveillance program were found positive for antibodies against Yellow Fever Virus (YFV). In order to characterize patients with acute febrile jaundice negative for YFV, we collected 255 sera between January to December 2019. We screened for HBV antigens, and antibodies against HCV and HEV. The seroprevalences observed were 10.6% (27/255) for HBV, 2% (5/255) for HCV, 17.3% (44/255) for HEV IgG, 4.3% (11/255) for HEV IgM, and 12.5% (32/255) for both IgG and IgM HEV. Prevalence of HEV was significantly higher in females than males (p < 0.01). HEV IgG prevalence was highest in those 20–29 years old, but the highest incidence rate (IgM positive) was in children 0–9 years old. Exposure to HEV was higher in the Sahelian zone (55.8%, 95% CI: 40.97–70.66) than in the Sudanese zone (30.2%, 95% CI: 24.01–36.37, p = 0.003). The high prevalence rates and hepatitis virus diversity underline the challenge of routine clinical diagnosis in Chad’s Yellow Fever surveillance program.

Brucellosis, Rift Valley fever (RVF) and Q fever are zoonoses prevalent in many developing countries, causing a high burden on human and animal health. Only a few studies are available on these among agro-pastoralist communities and their livestock in Chad. The objective of our study was to estimate brucellosis, RVF and Q fever seroprevalence among Chadian agro-pastoralist communities and their livestock, and to investigate risk factors for seropositivity. We conducted a multi-stage cross-sectional serological survey in two rural health districts, Yao and Danamadji (966 human and 1041 livestock (cattle, sheep, goat and equine) samples)). The true seroprevalence were calculated applying a Bayesian framework to adjust for imperfect diagnostic test characteristics and accounting for clustering in the study design. Risk factors for each of the zoonotic diseases were estimated using mixed effects logistic regression models. The overall prevalence for brucellosis, Q fever and RVF combined for both regions was estimated at 0.2% [95% credibility Interval: 0–1.1], 49.1% [%CI: 38.9–58.8] and 28.1% [%CI: 23.4–33.3] in humans, and 0.3% [%CI: 0–1.5], 12.8% [%CI: 9.7–16.4] and 10.2% [%CI: 7.6–13.4] in animals. Risk factors correlating significantly with the respective disease seropositivity were sex for human brucellosis, sex and Q fever co-infection for animal brucellosis, age for human Q fever, species and brucellosis co-infection for animal Q fever, age and herd-level animal RVF seroprevalence within the same cluster for human RVF, and cluster-level human RVF seroprevalence within the same cluster for animal RVF. In Danamadji and Yao, Q fever and RVF are notably seroprevalent among agro-pastoralist human and animal communities, while brucellosis appears to have a low prevalence. Correlation between the seroprevalence between humans and animals living in the same communities was detected for RVF, highlighting the interlinkage of human and animal transmissible diseases and of their health, highlighting the importance of a One Health approach.

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.

Background Chad with 7,698 confirmed cases of infection and 194 deaths since the beginning of the COVID-19 pandemic, is one of the African countries with the lowest reported case numbers. However, this figure likely underestimates the true spread of the virus due to the low rate of diagnosis. The high rate of asymptomatic infections reflects the reality of SARS-CoV-2 transmission in Chad. In this study, we estimated the seroprevalence and identified factors associated with SARS-CoV-2 infection. Methods A cross-sectional study was conducted between September 2022 and February 2023. A total of 1,290 plasma samples were collected from outpatient attendees at Health Facilities located in 11 provinces of Chad and tested by ELISA method, for the presence of IgG antibodies to SARS-CoV2 nucleocapsid (N) protein. KoboToolbox was used to gather data from the participants and data were analyzed using STATA 16. Results The overall seroprevalence was 83.0% [95% CI = 81.6%—85.5%], with variations between provinces, ranging from 99.2% [95% CI = 94.0%—100%] in Moundou (Southern Chad) to 46.8% [95% CI = 36.0% -57.1%] in Biltine (Eastern Chad). Factors associated with the seroprevalence included military occupation (OR = 0.37 CI [0.80–1.77] p  = 0.025) and age group between 55–64 years (OR = 0.33 CI [0.15–0.72] p  = 0.005). While, other factors, such as gender and age were not significantly associated with seroprevalence. Conclusion Our results indicated that, the seroprevalence of COVID-19 in Chad is among the highest in Sub-Saharan Africa. These estimates could guide the response and public health policy decisions, enhancing the management of future outbreaks involving respiratory pathogens.

Background Group A Rotaviruses (RVA) is one of the most common causes of severe diarrhoea in infants and children under 5 years of age. Unlike many countries in the world where RVA surveillance/control is active, in Chad , there is currently no applied RVA immunization program and surveillance strategy. The present study aims to determine the prevalence and associated risk factors of RVA gastroenteritis among children under five years of age in N’Djamena. Method This study comprised two parts: (1) A cross-sectional study carried in four hospitals in N’Djamena between August and November 2019, to determine infection risk factors and evidence of RVA infection among children aged five and below, consulted or hospitalized for diarrhea. An ELISA based RVA VP6 protein detection was used to determine RVA infection prevalence. Infection results and sociodemographic data were statistically analysed to determine RVA infection risk factors. (2) A retrospective study that consisted of analysing the records of stool examinations of the period from January 2016 to December 2018, to determine the prevalence of infectious gastroenteritis among the target population. Results For the cross-sectional study, RVA infection prevalence was 12.76% (18/141) with males (61.11%) being more affected (sex ratio: 1.57). Children below 12 months were the most affected age group (44.44%) and 44.4% were malnourished. The mean Vesikari score shows that 38.8% of children have a high severity level and 41.1% have a moderate level. For the retrospective study, 2,592 cases of gastroenteritis hospitalization were analysed; 980 out of 2,592 cases (37.81%) of hospitalization due to diarrhoea were due to diarrhoeagenic pathogens including Emtamoeba hystolitica, Gardia lamblia, Trichomonas hominis, Hymenolepis nana, Escherichia coli, Shigella spp, Proteus mirabilis , and Klebsiella oxytoca . Cases of diarrhoea with negative pathogen search were 1,612 cases (62.19%). The diarrhoea peak was observed during the dry seasons, and the age group under 11 months was the most affected was (57.3%). Conclusion This study describes the evidence of RVA infection among diarrhoeic children below five years of age in N’Djamena, thus indicates a serious health burden. Malnourishment younger age was the higher risk factor. Further studies are needed to determine the circulating strains prior to considering introduction of RVA vaccine and setup a routine rotavirus surveillance in Chad.

Free-roaming domestic dogs (FRDD), as vectors of zoonotic diseases, are of high relevance for public health. Understanding roaming patterns of dogs can help to design disease control programs and disease transmission simulation models. Studies on GPS tracking of dogs report stark differences in recording periods. So far, there is no accepted number of days required to capture a representative home range (HR) of FRDD. The objective of this study was to evaluate changes in HR size and shape over time of FRDD living in Chad, Guatemala, Indonesia and Uganda and identify the period required to capture stable HR values. Dogs were collared with GPS units, leading to a total of 46 datasets with, at least, 19 recorded days. For each animal and recorded day, HR sizes were estimated using the Biased Random Bridge method and percentages of daily change in size and shape calculated and taken as metrics. The analysis revealed that the required number of days differed substantially between individuals, isopleths, and countries, with the extended HR (95% isopleth value) requiring a longer recording period. To reach a stable HR size and shape values for 75% of the dogs, 26 and 21 days, respectively, were sufficient. However, certain dogs required more extended observational periods.

Influenza-like Illness (ILI) is a medical diagnosis of possible influenza or another respiratory illness with a common set of symptoms. The deaths of four schoolchildren, during a pandemic influenza outbreak in December 2017 in Ghana, raised doubts about the ILI surveillance system's performance. We evaluated the ILI surveillance system in the Greater Accra region, Ghana, to assess the system's attributes and its performance on set objectives. CDC guidelines were used to evaluate the data of the ILI surveillance system between 2013 and 2017. We interviewed the surveillance personnel on the system's description and operation. Additionally, routinely entered ILI data from the National Influenza Center provided by the six sentinel sites in Accra was extracted. We sampled and reviewed 120 ILI case-investigation forms from these sites. Surveillance activities were examined on system's performance indicators, each being scored on a scale of 1 to 3 (poorest to best performance). All population and age groups were under ILI surveillance over the period evaluated. Overall, 2948 suspected case-patients, including 392 (13.3%) children under-five were reported, with 219 being positive for influenza virus (Predictive value positive = 7.4%). The predominant influenza subtype was H3N2, recorded in 90 (41.1%) of positive case-patients. The system only met two out of its four objectives. None of the six sentinel sites consistently met their annual 260 suspected case-detection quota. Samples reached the laboratory on average 48 hours after collection and results were disseminated within 7 days. Of 120 case-investigation forms sampled, 91 (76.3%) were completely filled in. The ILI surveillance system in the Greater Accra region is only partially meeting its objectives. While it is found to be sensitive, representative and timely, the data quality was sub-optimal. We recommend the determination of thresholds for alert and outbreak detection and ensuring that sentinel sites meet their weekly case-detection targets.

Background Demand side barriers to vaccination among rural and hard-to-reach populations in Chad are not yet well understood. Although innovative approaches such as linking human and animal vaccination increase vaccination uptake among mobile pastoralist communities, vaccination coverage in these communities is still lower than for rural settled populations. We hypothesize that mobile pastoralists’ communities in Chad face specific demand side barriers to access vaccination services. Understanding the factors that caregivers in these communities consider, explicitly or implicitly, in order to decide whether or not to vaccinate a child, in addition to understanding the provider’s perspectives, are essential elements to tailor vaccination programmes towards increasing vaccination acceptance and uptake. Methods We conducted a qualitative study in a rural health district in southern Chad in April 2016 with 12 key informant in-depth interviews and four focus group discussions (FGDs) including 35 male and female participants. Participants in the study included caregivers, traditional chiefs, local and religious leaders from mobile pastoralist communities, and health officials and staff. We conducted a content analysis using a pre-defined set of categories for vaccine hesitancy covering issues on harmful effects of vaccination, mistrust with vaccination programmes/services, issues with the health system and other issues. Results The groups of demand side barriers reported most frequently in focus group discussions were mistrust on the expanded programme on immunization (EPI) and polio vaccination outreach services (53%, n  = 94), followed by health system issues (34%, n = 94), and concerns related to potential harm of vaccines (13%, n = 94). Concerns identified by caregivers, health professionals and community leaders followed a similar pattern with issues on programme mistrust being most frequently reported and issues with harm least frequently reported. None of the health professionals reported concerns about vaccinations being potentially harmful. Conclusion Mobile pastoralist communities face specific demand side barriers to vaccination. Understanding these barriers is essential to reduce vaccine hesitancy and increase vaccination uptake. Local health systems must plan for the periodic presence of pastoralist communities in their zones of responsibility and create more mutual trust.