Seroepidemiology of Crimean-Congo Haemorrhagic Fever among cattle in Cameroon: Implications from a One Health perspective

Ticks (Acari: Ixodidae) and tick-borne diseases in Cameroon: Current understanding and future directions for more comprehensive surveillance

Despite the high burden of human and animal infectious diseases in Cameroon, implementing integrative approaches to managing and controlling arthropods and their pathogens remains challenging. Surveillance should be designed to detect diseases and provide relevant field-based data for developing and implementing effective control measures to prevent outbreaks before significant public and animal health consequences can occur. Nowadays, ticks are considered the primary vectors of animal diseases in the world, and the second vector of human diseases after mosquitoes. Knowledge of their biodiversity and distribution in any given area is a crucial step towards a better implementation of control strategies. The infections transmitted by ticks remain poorly known or underestimated in Cameroon. Despite the existence of several studies on ticks and associated pathogens, no single review to date summarises all the data available in this field in Cameroon. Following a comprehensive literature search, an inventory of the diversity and distribution of ticks, as well as the different tick-borne diseases (viral, bacteria and protozoa) found in Cameroon was prepared. To date, about 71 species, comprising ten Amblyomma species., eight Hyalomma spp., 26 Rhipicephalus spp., 11 Haemaphysalis spp., seven Ixodes spp., five Aponomma spp. (currently the Bothriocroton species), one Dermacentor, and four soft tick species of minimal or unknown medical and veterinary importance, namely Argas persicus, A. arboreus, Carios vespertilionis, and Ogadenus brumpti have been collected in Cameroon. Many zoonotic tick-borne diseases, such as babesiosis, theileriosis, anaplasmosis, ehrlichiosis, rickettsioses, and Q fever have been reported in the country. Knowledge about tick species and their distribution will aid in designing integrated vector management programs to monitor tick-borne diseases in Cameroon.

Determinants of viral haemorrhagic fever risk in Africa's tropical moist forests: A scoping review of spatial, socio-economic, and environmental factors

BACKGROUND

Viral haemorrhagic fevers (VHFs) are identified by international health authorities as priorities for research and development, as they pose a threat to global health and economy. VHFs are zoonotic diseases whose acute forms in humans present a haemorrhagic syndrome and shock, with mortality rates of up to 90%. This work aims at synthetizing existing knowledge on spatial and spatially aggregable determinants that support the emergence and maintenance of VHFs in African countries covered by tropical moist forest, to better identify and map areas at risk.

METHODOLOGY/PRINCIPAL FINDINGS

Using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA-ScR) guidelines, extension for scoping reviews, we searched the PubMed, Embase, CAB Abstracts, and Scopus databases. English and French peer-reviewed documents were retrieved using Boolean logic and keyword search terms. The analysis of 79 articles published between 1993 and 2023 offers a comprehensive overview of the complex interactions among abiotic, biotic, demographic, socio-economic, cultural, and political risk factors in driving the emergence and maintenance of VHFs in African countries covered by tropical moist forests. Human-to-human transmission is mainly driven by socio-economic, political, and demographic factors, whereas zoonotic spillover is determined by almost all groups of factors, especially those of an anthropogenic nature.

CONCLUSIONS/SIGNIFICANCE

Many questions remain unanswered regarding the epidemiology of VHFs in tropical forests. By elucidating spatially relevant determinants which have already been studied, this review seeks to advance VHFs hotspot predictions, risk mapping for disease surveillance and control systems improvement.

Development of a Luciferase Immunosorbent Assay for Detecting Crimean-Congo Hemorrhagic Fever Virus IgG Antibodies Based on Nucleoprotein

Crimean-Congo hemorrhagic fever (CCHF) is a serious tick-borne disease with a wide geographical distribution. Classified as a level 4 biosecurity risk pathogen, CCHF can be transmitted cross-species due to its aerosol infectivity and ability to cause severe hemorrhagic fever outbreaks with high morbidity and mortality. However, current methods for detecting anti-CCHFV antibodies are limited. This study aimed to develop a novel luciferase immunosorbent assay (LISA) for the detection of CCHFV-specific IgG antibodies. We designed specific antigenic fragments of the nucleoprotein and evaluated their sensitivity and specificity in detecting IgG in serum samples from mice and horses. In addition, we compared the efficacy of our LISA to a commercial enzyme-linked immunosorbent assay (ELISA). Our results demonstrated that the optimal antigen for detecting anti-CCHFV IgG was located within the stalk cut-off domain of the nucleoprotein. The LISA exhibited high specificity for serum samples from indicated species and significantly higher sensitivity (at least 128 times) compared with the commercial ELISA. The proposed CCHFV-LISA has the potential to facilitate serological diagnosis and epidemiological investigation of CCHFV in natural foci, providing valuable technical support for surveillance and early warning of this disease.

Crimean Congo hemorrhagic fever virus exposure among febrile patients, cattle herders, and cattle herds in Cameroon

PROBLEM ADDRESSED

Crimean Congo hemorrhagic fever (CCHF) is a tick-borne disease with high fatality rates and an expansive geographic distribution, yet disease prevalence data in Cameroon is lacking.

OBJECTIVE

This study aimed to determine CCHF virus (CCHFV) seroprevalence and tick distribution among cattle herders and febrile patients in West and Centre Cameroon.

METHODS AND APPROACH

Two cross-sectional serological studies of human and cattle were conducted from October to December 2021 and from June to July 2022, which included the collection of ticks. Enzyme-linked immunosorbent assay (ELISA) were used to detect anti-CCHFV antibodies, while a knowledge, attitudes, and practice (KAP) survey assessed tick and tickborne disease related knowledge and behaviors among herders. Tick identification used morphological keys.

RESULTS

The KAP survey showed adequate tick knowledge (94.5 %) among herders but poor understanding of disease transmission, with favorable attitudes towards tick control (24.7 %) but inadequate implementation. Rhipicephalus annulatus (64.1 %) predominated among the 1,296 ticks collected during each rainy season. Among cattle, 27.4 % were seropositive, and seropositivity was associated with specific villages, cattle age (>4 years), and female sex. Herders had a 17.8 % seroprevalence, while febrile patients had 8.3 %, with higher rates in those >20 years old for both groups. Self-reported tick removal by herders after contact and grazing may increase CCHFV exposure.

CONCLUSIONS

This study confirms CCHFV circulation in rural West Cameroon and unexpected exposure risk in Yaounde, highlighting the need for active entomological surveillance and preventive measures in transhumance and cattle market activities. Establishing an occupation-based surveillance system can help identify CCHFV hotspots to prevent outbreaks.

Crimean-Congo haemorrhagic fever outbreak in Northern Senegal in 2022: Prevalence of the virus in livestock and ticks, associated risk factors and epidemiological implications

OBJECTIVE

Crimean-Congo haemorrhagic fever (CCHF) is a severe zoonotic arboviral disease that occurs widely in Eastern and Western Europe, Asia and Africa. The disease is becoming of growing public health importance in Senegal. However, analysis of tick infestation, CCHF virus (CCHFV) circulation extent and risk factors during ongoing outbreak are scarce. A thorough outbreak investigation was carried out during a CCHF outbreak in Podor (Northern Senegal) in August 2022.

METHODS

Ticks and blood samples were collected from animals (cattle, goats and sheep) randomly selected from confirmed CCHF human cases houses, neighbourhoods and surrounding villages. Blood samples were tested for CCHFV antibodies using a commercial enzyme-linked immunosorbent assay (ELISA) test. Tick samples were screened for CCHFV RNA by RT-PCR.

RESULTS

Overall, tick infestation rate (TIR) and CCHFV seroprevalence of livestock were 52.12% (95% confidence interval (CI): 45.54%-58.64%) and 43.28% (95% CI: 36.33%-50.44%), respectively. The TIRs were 87.7% in cattle, 57.6% in sheep and 20.0% in goats. These rates were significantly associated with location, host species and tick control (p < 0.001) but not with animal age and sex (p > 0.7). CCHFV seroprevalence was 80.4% (95% CI: 67.57%-89.77%) in cattle, 35.4% (95% CI: 25.00%-47.01%) in sheep and 21.2% (95% CI: 12.11%-33.02%) in goats. Age, sex, location, animal host and presence of ticks were significantly associated to the presence of antibodies. The 950 ticks collected included among other species, Hyalomma impeltatum (48.84%) and H. rufipes (10.21%). Five pools of Hyalomma ssp. were found CCHFV RT-PCR positive. These infected ticks included 0.86% (4/464) of H. impeltatum collected on cattle and sheep and 1.03% (1/97) of H. rufipes collected on a sheep.

CONCLUSIONS

To our knowledge, this is the first report on the extend of tick infestation and CCHFV infection in livestock during an outbreak in Senegal. The results highlight the risk of human infections and the importance of strengthening vector, animal and human surveillance as well as tick control measures in this area to prevent CCHF infections in humans.

Seromolecular survey and risk factor analysis of Crimean-Congo haemorrhagic fever orthonairovirus in occupationally exposed herdsmen and unexposed febrile patients in Kwara State, Nigeria

Crimean-Congo haemorrhagic fever virus (CCHFV) is a globally significant tick-borne zoonotic pathogen that causes fatal haemorrhagic disease in humans. Despite constituting an ongoing public health threat, limited research exists on the presence of CCHFV among herdsmen, an occupationally exposed population that has prolonged contact with ruminants and ticks. This cross-sectional study, conducted between October 2018 and February 2020 in Kwara State, Nigeria, was aimed at assessing CCHFV seroprevalence among herdsmen and non-herdsmen febrile patients, and identifying the associated risk factors. Blood samples from herdsmen (n = 91) and febrile patients in hospitals (n = 646) were analyzed for anti-CCHFV IgG antibodies and CCHFV S-segment RNA using ELISA and RT-PCR, respectively. Results revealed a remarkably high CCHFV seroprevalence of 92.3% (84/91) among herdsmen compared to 7.1% (46/646) in febrile patients. Occupational risk factors like animal and tick contact, tick bites, and hand crushing of ticks significantly contributed to higher seroprevalence in the herdsmen (p<0.0001). Herdsmen were 156.5 times more likely (p<0.0001) to be exposed to CCHFV than febrile patients. Notably, the odds of exposure were significantly higher (OR = 191.3; p<0.0001) in herdsmen with a history of tick bites. Although CCHFV genome was not detectable in the tested sera, our findings reveal that the virus is endemic among herdsmen in Kwara State, Nigeria. CCHFV should be considered as a probable cause of febrile illness among humans in the study area. Given the nomadic lifestyle of herdsmen, further investigations into CCHF epidemiology in this neglected population are crucial. This study enhances our understanding of CCHFV dynamics and emphasizes the need for targeted interventions in at-risk communities.

Serological and molecular epidemiological investigation of Mediterranean spotted fever in Yunnan Province, China

OBJECTIVES

Given the limited research and its potential hazards, the study aimed to determine the prevalence of Mediterranean spotted fever (MSF) caused by Rickettsia conorii (R. conorii), a tick-borne disease, in Yunnan Province, China.

METHODS

Through stratified sampling across five distinct regions in Yunnan, 5358 blood samples were obtained from the general healthy population. Enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), and Polymerase chain reaction (PCR) were employed for analysis.

RESULTS

IFA identified 27 (0.50%) subjects with immunoglobulin G (IgG) positivity; none were positive for immunoglobulin M (IgM) via ELISA. PCR detected one individual with R. conorii outer membrane protein A (ompA). Significant seroprevalence variation was observed, particularly in Southern Yunnan (P = 0.032), with R. conorii subsp. conorii confirmed in the PCR-positive sample.

CONCLUSIONS

This research reveals a correlation between MSF prevalence, geography, and climate in Yunnan. The paucity of prior studies underscores MSF's potential diagnostic challenges in the region. Comprehensive understanding of the pathogen's distribution is pivotal for intervention. Given the study's scope and Yunnan's unique setting, additional research is advocated.

Transmission Dynamics of Crimean-Congo Haemorrhagic Fever Virus (CCHFV): Evidence of Circulation in Humans, Livestock, and Rodents in Diverse Ecologies in Kenya

Crimean-Congo haemorrhagic fever virus (CCHFV) is the causative agent of CCHF, a fatal viral haemorrhagic fever disease in humans. The maintenance of CCHFV in the ecosystem remains poorly understood. Certain tick species are considered as vectors and reservoirs of the virus. Diverse animals are suspected as amplifiers, with only scarce knowledge regarding rodents in virus epidemiology. In this study, serum samples from febrile patients, asymptomatic livestock (cattle, donkeys, sheep, and goats), and peridomestic rodents from Baringo (Marigat) and Kajiado (Nguruman) counties within the Kenyan Rift Valley were screened for acute CCHFV infection by RT-PCR and for CCHFV exposure by ELISA. RT-PCR was performed on all livestock samples in pools (5-7/pool by species and site) and in humans and rodents individually. CCHFV seropositivity was significantly higher in livestock (11.9%, 113/951) compared to rodents (6.5%, 6/93) and humans (5.9%, 29/493) (p = 0.001). Among the livestock, seropositivity was the highest in donkeys (31.4%, 16/51), followed by cattle (14.1%, 44/310), sheep (9.8%, 29/295) and goats (8.1%, 24/295). The presence of IgM antibodies against CCHFV was found in febrile patients suggesting acute or recent infection. CCHFV RNA was detected in four pooled sera samples from sheep (1.4%, 4/280) and four rodent tissues (0.83%, 4/480) showing up to 99% pairwise nucleotide identities among each other. Phylogenetic analyses of partial S segment sequences generated from these samples revealed a close relationship of 96-98% nucleotide identity to strains in the CCHFV Africa 3 lineage. The findings of this study suggest active unnoticed circulation of CCHFV in the study area and the involvement of livestock, rodents, and humans in the circulation of CCHFV in Kenya. The detection of CCHF viral RNA and antibodies against CCHFV in rodents suggests that they may participate in the viral transmission cycle.

Molecular and serological evidence of Crimean-Congo hemorrhagic fever orthonairovirus prevalence in livestock and ticks in Cameroon

Introduction

Despite a high fatality rate in humans, little is known about the occurrence of Crimean-Congo hemorrhagic fever virus (CCHFV) in Cameroon. Hence, this pioneer study was started with the aim of determining the prevalence of CCHFV in domestic ruminants and its potential vector ticks in Cameroon.

Methods

A cross-sectional study was carried out in two livestock markets of Yaoundé to collect blood and ticks from cattle, sheep, and goats. CCHFV-specific antibodies were detected in the plasma using a commercial ELISA assay and confirmed using a modified seroneutralization test. Ticks were screened for the presence of orthonairoviruses by amplification of a fragment of the L segment using RT-PCR. Phylogeny was used to infer the genetic evolution of the virus.

Results

Overall, 756 plasma samples were collected from 441 cattle, 168 goats, and 147 sheep. The seroprevalence of CCHFV was 61.77% for all animals, with the highest rate found in cattle (433/441, 98.18%) followed by sheep (23/147, 15.65%), and goats (11/168, 6.55%), (p-value < 0.0001). The highest seroprevalence rate was found in cattle from the Far North region (100%). Overall, 1500 ticks of the Rhipicephalus (773/1500, 51.53%), Amblyomma (341/1500, 22.73%), and Hyalomma (386/1500, 25.73%) genera were screened. CCHFV was identified in one Hyalomma truncatum pool collected from cattle. Phylogenetic analysis of the L segment classified this CCHFV strain within the African genotype III.

Conclusion

These seroprevalence results call for additional epidemiological studies on CCHFV, especially among at-risk human and animal populations in high-risk areas of the country.

Prevalence of Crimean-Congo haemorrhagic fever in livestock following a confirmed human case in Lyantonde district, Uganda

BACKGROUND

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne viral infection, characterized by haemorrhagic fever in humans and transient asymptomatic infection in animals. It is an emerging human health threat causing sporadic outbreaks in Uganda. We conducted a detailed outbreak investigation in the animal population following the death from CCHF of a 42-year-old male cattle trader in Lyantonde district, Uganda. This was to ascertain the extent of CCHF virus (CCHFV) circulation among cattle and goats and to identify affected farms and ongoing increased environmental risk for future human infections.

METHODS

We collected blood and tick samples from 117 cattle and 93 goats, and tested these for anti-CCHFV antibodies and antigen using an enzyme-linked immunosorbent assay (ELISA), quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and target enrichment next generation sequencing.

RESULTS

CCHFV-specific IgG antibodies were detected in 110/117 (94.0%) cattle and 83/93 (89.3%) goats. Animal seropositivity was independently associated with female animals (AOR = 9.42, P = 0.002), and animals reared under a pastoral animal production system (AOR = 6.02, P = 0.019] were more likely to be seropositive than tethered or communally grazed animals. CCHFV was detected by sequencing in Rhipicephalus appendiculatus ticks but not in domestic animals.

CONCLUSION

This investigation demonstrated very high seroprevalence of CCHFV antibodies in both cattle and goats in farms associated with a human case of CCHF in Lyantonde. Therefore, building surveillance programs for CCHF around farms in this area and the Ugandan cattle corridor is indicated, in order to identify opportunities for case prevention and control.

Infestation rates, seasonal distribution, and genetic diversity of ixodid ticks from livestock of various origins in two markets of Yaoundé, Cameroon

Little is known about the impact of ticks on livestock and humans in Cameroon. This study aimed to determine the prevalence, seasonal variation, and genetic diversity of hard ticks in the country. Ticks were collected during a cross-sectional survey on domestic livestock in two markets of Yaoundé in 2019 and 2020 and identified using morphological keys, 16S ribosomal DNA, (16S rDNA), and the cytochrome c oxidase subunit 1 (Cox1) genes. The infestation rates were 39.18%, 11.53%, and 2.74% in cattle, sheep, and goats respectively. Three genera of ticks were identified, Rhipicephalus, Amblyomma, and Hyalomma comprising eleven tick species. The main species were Rhipicephalus decoloratus (30.25%), R. microplus (24.43%), and Amblyomma variegatum (12.96%). Rhipicephalus spp. (81.31%) and Amblyomma variegatum (51.54%) were abundant during the rainy season, while Hyalomma spp. (83.86%) during the dry season (p-value <0.00001). Cox1 and 16S rDNA analysis showed a high level of genetic diversity among tick species with sequences close to those observed across Africa. Phylogenetic analysis revealed that our R. microplus belong to clade A and we identified R. sanguineus s.l. as R. linnea. This study shows a high tick infestation rate in cattle, while low in small ruminants with an extensive diversity of tick species, including several known vectors of important tick-borne diseases.

A Cross-Sectional, Population-Based, Seroepidemiological Study of Rift Valley Fever in Cameroonian Cattle Populations

Rift Valley fever (RVF) is an important emerging zoonoses causing abortion and neonatal deaths in livestock and hemorrhagic fever in humans. It is typically characterized by acute epidemics with abortion storms often preceding human disease and these events have been associated with the El Niño weather cycles. Outside of areas that experience epidemics, little is known about its epidemiology. Here, we present results from a serological study using biobank samples from a study of cattle conducted in 2013 at two sites in Cameroon. A total of 1,458 cattle from 100 herds were bled and sera screened using a commercially available RVF ELISA. The overall design-adjusted animal-level apparent seroprevalence of RVF exposure for the Northwest Region (NWR) of Cameroon was 6.5% (95% CI: 3.9–11.0) and for the Vina Division (VIN) of the Adamawa Region was 8.2% (95% CI: 6.2–11.0). The age-stratified serological results were also used to estimate the force of infection, and the age-independent estimates were 0.029 for the VIN and 0.024 for the NWR. The effective reproductive number was ~1.08. Increasing age and contact with wild antelope species were associated with an increased risk of seropositivity, while high altitudes and contact with buffalo were associated with a reduced risk of seropositivity. The serological patterns are more consistent with an endemical stability rather than the more typical epidemic patterns seen in East Africa. However, there is little surveillance in livestock for abortion storms or in humans with fevers in Cameroon, and it is, therefore, difficult to interpret these observations. There is an urgent need for an integrated One Health approach to understand the levels of human- and livestock-related clinical and asymptomatic disease and whether there is a need to implement interventions such as vaccination.

[Crimean-Congo hemorrhagic fever]

Crimean-Congo hemorrhagic fever (CCHF) is an acute febrile illness with a high case fatality rate caused by the infection with Crimean-Congo hemorrhagic fever virus (CCHFV). The disease is endemic to a wide regions from the African continent to Asia through Europe. CCHFV is maintained in nature between Hyalomma species ticks and some species of animals. Humans are infected with CCHFV from CCHFV-positive tick bite or through a close contact with viremic animals in clucling hum am patients with CCHF. The CCHF-endemic regions depend on the distribution of the species of ticks such as Hyalomma species ticks, main vectors for CCHFV. There have been no confirmed cases of CCHF patients in Japan so far. CCHF is one of the zoonotic virus infections. Main clinical signs of the disease in humans are fever with nonspecific symptoms, and hemorrhage and deterioration in consciousness appear in severe cases. CCHF is classified in the disease category of viral hemorrhagic fevers, which include ebolavirus disease. Viral tick-borne diseases including tick-borne encephalitis, severe fever with thrombocytopenia syndrome, and Yezo virus infection, which has recently been discovered as a novel bunyavirus infection in Hokkaido, Japan, are becoming major concerns for public health in Japan. Trends of CCHF in terms of epidemiology should closely be monitored.