Risk factors for Crimean-Congo Haemorrhagic Fever (CCHF) virus exposure in farming communities in Uganda

Prevalence of Crimean-Congo Haemorrhagic Fever virus and Ganjam virus among livestock & ticks in Wayanad, Kerala

The Western Ghat region of Kerala has abundant flora and domestic and wild animal species that provide an ideal ecological niche for the ticks. Kyasanur Forest Disease virus (KFDV), a zoonotic tick-borne virus causing Haemorrhagic fever, commonly known as monkey fever is prevalent in the area. The tick infestations have been documented in the majority of household animals in Wayanad and risks are further amplified as the majority of the animals reared, graze in the adjoining forest areas and these animals are often housed in and around farmer's dwellings. Therefore, the farmers are at high risk of contracting deadly tick-borne diseases, and surveillance in animals can act as an indicator of disease hotspots. Even though the tick-borne KFDV is endemic to the area, the surveillance data on other significant zoonotic tick-borne viruses such as CCHFV and GANV are scanty. Overall CCHFV seroprevalence of 2.33 was reported amongst livestock sampled. Species-wise percent seropositivity was 1.01 and 5.10 in cattle and goats, respectively. The study revealed the presence of ticks belonging to 3 genera viz. Rhipicephalus, Amblyomma, and Haemaphysalis. Despite the CCHFV seroprevalence, CCHFV and GANV could not be detected in ticks. Even though ticks were negative for the CCHFV genome, seroprevalence in adjoining taluks indicates the local virus circulation. Therefore serological as well as molecular investigation with a large number of samples collected at the peak of tick activity across the western ghat would help identify the potential hotspot for CCHFV.

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.

Control strategies for emerging infectious diseases: Crimean-Congo hemorrhagic fever management

Background and Aims

Crimean-Congo Hemorrhagic Fever (CCHF) is a significant public health concern transmitted by ticks. This study seeks to thoroughly grasp the epidemiology and transmission patterns of CCHF, which is caused by the CCHF virus (CCHFV), a member of the Nairovirus genus in the Bunyaviridae family.

Methods

The study investigates the global distribution and endemicity of CCHF, its mortality rates, modes of transmission (including tick bites, contact with infected animal blood, and limited person-to-person transmission), and factors influencing its prevalence across different regions. Genetic diversity within CCHFV and its impact on transmission dynamics are explored, along with efforts to control the disease through tick prevention, antiviral treatment, and the development of vaccines and diagnostics.

Results

CCHFV exhibits widespread distribution, particularly in the Middle East, Africa, Asia, and Eastern Europe, with an overall mortality rate of approximately 30% and a case fatality rate ranging from 10% to 40%. Transmission occurs primarily through tick bites and contact with infected animal blood, with limited person-to-person transmission. Livestock workers, slaughterhouse employees, and animal herders in endemic areas are most affected by their frequent interaction with sick animals and ticks. Genetic diversity within CCHFV contributes to variations in transmission dynamics, complicating control efforts. Antiviral ribavirin shows efficacy in treating CCHF infection.

Conclusion

This study underscores the importance of further research to understand the enzootic environment, transmission routes, and genetic diversity of CCHFV for effective control measures, including the development of vaccines, treatment options, and diagnostics.

Viruses of free-roaming and hunting dogs in Uganda show elevated prevalence, richness and abundance across a gradient of contact with wildlife

Domestic dogs (Canis lupus familiaris) live with humans, frequently contact other animals and may serve as intermediary hosts for the transmission of viruses. Free-roaming dogs, which account for over 70% of the world's domestic dog population, may pose a particularly high risk in this regard. We conducted an epidemiological study of dog viromes in three locations in Uganda, representing low, medium and high rates of contact with wildlife, ranging from dogs owned specifically for traditional hunting in a biodiversity and disease 'hotspot' to pets in an affluent suburb. We quantified rates of contact between dogs and wildlife through owner interviews and conducted canine veterinary health assessments. We then applied broad-spectrum viral metagenomics to blood plasma samples, from which we identified 46 viruses, 44 of which were previously undescribed, in three viral families, Sedoreoviridae, Parvoviridae and Anelloviridae. All 46 viruses (100 %) occurred in the high-contact population of dogs compared to 63 % and 39 % in the medium- and low-contact populations, respectively. Viral prevalence ranged from 2.1 % to 92.0 % among viruses and was highest, on average, in the high-contact population (22.3 %), followed by the medium-contact (12.3 %) and low-contact (4.8 %) populations. Viral richness (number of viruses per dog) ranged from 0 to 27 and was markedly higher, on average, in the high-contact population (10.2) than in the medium-contact (5.7) or low-contact (2.3) populations. Viral richness was strongly positively correlated with the number of times per year that a dog was fed wildlife and negatively correlated with the body condition score, body temperature and packed cell volume. Viral abundance (cumulative normalized metagenomic read density) varied 124-fold among dogs and was, on average, 4.1-fold higher and 2.4-fold higher in the high-contact population of dogs than in the low-contact or medium-contact populations, respectively. Viral abundance was also strongly positively correlated with the number of times per year that a dog was fed wildlife, negatively correlated with packed cell volume and positively correlated with white blood cell count. These trends were driven by nine viruses in the family Anelloviridae, genus Thetatorquevirus, and by one novel virus in the family Sedoreoviridae, genus Orbivirus. The genus Orbivirus contains zoonotic viruses and viruses that dogs can acquire through ingestion of infected meat. Overall, our findings show that viral prevalence, richness and abundance increased across a gradient of contact between dogs and wildlife and that the health status of the dog modified viral infection. Other ecological, geographic and social factors may also have contributed to these trends. Our finding of a novel orbivirus in dogs with high wildlife contact supports the idea that free-roaming dogs may serve as intermediary hosts for viruses of medical importance to humans and other animals.

Epidemiologic Survey of Crimean-Congo Hemorrhagic Fever Virus in Suids, Spain

We conducted a cross-sectional study in wild boar and extensively managed Iberian pig populations in a hotspot area of Crimean-Congo hemorrhagic fever virus (CCHFV) in Spain. We tested for antibodies against CCHFV by using 2 ELISAs in parallel. We assessed the presence of CCHFV RNA by means of reverse transcription quantitative PCR protocol, which detects all genotypes. A total of 113 (21.8%) of 518 suids sampled showed antibodies against CCHFV by ELISA. By species, 106 (39.7%) of 267 wild boars and 7 (2.8%) of 251 Iberian pigs analyzed were seropositive. Of the 231 Iberian pigs and 231 wild boars analyzed, none tested positive for CCHFV RNA. These findings indicate high CCHFV exposure in wild boar populations in endemic areas and confirm the susceptibility of extensively reared pigs to CCHFV, even though they may only play a limited role in the enzootic cycle.

Serological Evidence of Crimean-Congo Haemorrhagic Fever in Livestock in the Omaheke Region of Namibia

This research examined the positivity ratio of Crimean-Congo haemorrhagic fever (CCHF) antibodies in cattle and sheep within Namibia's Omaheke region after a human disease outbreak in the same geographical area. A total of 200 samples (100 cattle and 100 sheep) were randomly collected from animals brought to two regional auction sites, and then tested using the ID Screen® CCHF Double Antigen Multi-Species Enzyme-Linked Immunosorbent Assay kit. Of the cattle samples, 36% tested positive, while 22% of the sheep samples were seropositive. The cattle had a significantly higher positivity ratio than sheep at the individual animal level (p = 0.0291). At the herd level, 62.5% of cattle herds and 45.5% of sheep flocks had at least one positive animal, but this difference was statistically insignificant (p = 0.2475). The fourteen cattle farms with at least one seropositive animal were dispersed across the Omaheke region. In contrast, the ten sheep farms with seropositive cases were predominantly situated in the southern half of the region. The study concluded that the CCHF is endemic in the Omaheke region and likely in most of Namibia, underscoring the importance of continued surveillance and preventive measures to mitigate the impact of CCHFV on animal health and potential spillover into human populations.

Investigating Crimean-Congo haemorrhagic fever virus seropositivity in camels and human behavioural risks in an abattoir in Nigeria

Crimean-Congo haemorrhagic fever virus (CCHFV) is an emerging viral pathogen with pandemic potential that is often misdiagnosed. Case fatality in low-resource settings could be up to 40% due to close contact between animals and humans. A two-year cross-sectional study was conducted in Fagge abattoir, Kano State, Nigeria, to estimate the seropositivity of CCHFV in camels using a commercial multi-species competitive enzyme-linked immunosorbent assay (ELISA). A closed-ended questionnaire was administered to the abattoir workers to assess their awareness, mitigation, and behavioural practices associated with CCHF. Of the 184 camels tested, 179 (97%) were seropositive for CCHFV (95% confidence interval (CI): 93.77, 99.11). The median (interquartile range (IQR)) age of respondents was 41 (35-52), with 62% having no education. Respondents had little knowledge about CCHFV and the concept of zoonotic disease. In this study, the high estimated prevalence of antibodies to CCHFV in camels highlights the heightened risk of transmission of CCHFV in Nigeria. Similarly, a concerning lack of knowledge and inadequate preventive practices, alongside a prevalence of high-risk behaviours associated with CCHF among abattoir workers, were noted in this study. Thus, there is an urgent need for comprehensive public health education and collaborative One Health strategies to avert the threats of spillover events.

Knowledge, attitudes, and practices regarding Crimean-Congo hemorrhagic fever in a high-prevalence suburban community, southeast of Iran

Crimean Congo Hemorrhagic Fever (CCHF) is a zoonotic viral disease with a high mortality rate. The World Health Organization has classified it as a high-priority pathogen due to its severity. To manage this disease, knowledge, attitude, and practices (KAP) of the community play an important role. This study was conducted in a suburban area in southeastern Iran, an endemic region with a high occurrence of CCHF. A cross-sectional study was performed among 176 livestock farmers in Zahedan suburb, and data were collected through an interviewer-administered questionnaire. Single-factor and multi-factor analysis of variance was used to identify factors related to participants' knowledge, attitude, and risk of CCHF. All statistical analyses were conducted using SPSS 24, and a significance level of p ≤ 0.05 was adopted to determine statistical significance. Overall, the knowledge level about CCHF was moderate. Participants demonstrated a better understanding of high-risk occupations compared to the transmission routes and symptoms of CCHF. Conversely, their knowledge about the prevention and treatment of CCHF was found to be inadequate. The participants exhibited a good attitude towards CCHF prevention; most considered it a dangerous disease, believed in the effectiveness of preventive measures, and demonstrated the ability to address perceived obstacles. High-frequency engagement in high-risk behaviors related to CCHF was observed among the study participants. In the multi-factor model, the most critical factors associated with knowledge were age (p = 0.044), CCHF infection (p = 0.047), and CCHF education (p = 0.004). Income (p = 0.001), keeping livestock at home (p = 0.028), and receiving CCHF education (p = 0.012) were the most critical factors associated with attitude toward the risk of CCHF. The most important factors related to CCHF high-risk behavior were age (p = 0.045), gender (p = 0.028), and handling livestock (p < 0.001). These findings emphasize the need for maintaining health educational efforts on CCHF.

Risk factors associated with Crimean-Congo hemorrhagic fever virus circulation among human, livestock and ticks in Mauritania through a one health retrospective study

BACKGROUND

Crimean Congo hemorrhagic fever (CCHF) is endemic in Southern Mauritania where recurrent outbreaks have been constantly observed since the 1980's. The present study is the first to assess CCHFV antibodies and RNA in humans.

METHODS

A retrospective study was conducted using 263 humans and 1380 domestic animals serum samples, and 282 tick specimens of Hyalomma genus collected from 54 settings in 12 provinces across Mauritania. Antibodies targeting CCHF viral nucleoprotein were detected in animal and human sera using double-antigen ELISA. CCHFV specific RNA was detected in human and animal sera as well as tick supernatants using a CCHFV real time RT-PCR kit. Individual characteristics of sampled hosts were collected at the same time and data were geo-referenced. Satellite data of several environmental and climatic factors, were downloaded from publicly available datasets, and combined with data on livestock mobility, animal and human density, road accessibility and individual characteristics to identify possible risk factors for CCHFV spatial distribution. To this end, multivariate logistic models were developed for each host category (human, small and large ruminants).

RESULTS

The overall CCHFV antibody prevalence was 11.8% [95% CI: 8.4-16.3] in humans (17.9% in 2020 and 5.4% in 2021; p = 0.0017) and 33.1% (95% CI: 30.1-36.3) in livestock. CCHFV-specific antibodies were detected in 91 (18.1%) out of 502 sheep, 43 (9.0%) out of 477 goats, 144 (90.5%) out of 161 dromedaries and 179 (74.6%) out of 240 cattle. CCHFV RNA was detected in only 2 (0.7%) sera out of 263 animals herders samples from Hodh El Gharbi province and in 32 (11.3%) out of 282 Hyalomma ticks. In humans as well as in animals, seropositivity was not associated with sex or age groups. The multivariate analysis determined the role of different environmental, climatic and anthropic factors in the spatial distribution of the disease with animal mobility and age being identified as risk factors.

CONCLUSION

Results of the present study demonstrate the potential risk of CCHF for human population in Mauritania primarily those living in rural areas in close vicinity with animals. Future studies should prioritize an integrative human and veterinary approach for better understanding and managing Crimean-Congo hemorrhagic fever.

Seroprevalence of Crimean Congo Hemorrhagic Fever Virus in Occupational Settings: Systematic Review and Meta-Analysis

Crimean Congo Hemorrhagic Fever (CCHF) Virus can cause a serious human disease, with the case fatality ratio previously estimated to be 30-40%. Our study summarized seroprevalence data from occupational settings, focusing on the following occupational groups: animal handlers, abattoir workers, farmers, healthcare workers, veterinarians, rangers, and hunters. Systematic research was performed on three databases (PubMed, EMBASE, MedRxiv), and all studies reporting seroprevalence rates (IgG-positive status) for CCHF virus were retrieved and their results were reported, summarized, and compared. We identified a total of 33 articles, including a total of 20,195 samples, i.e., 13,197 workers from index occupational groups and 6998 individuals from the general population. Pooled seroprevalence rates ranged from 4.751% (95% confidence intervals (95% CI) 1.834 to 11.702) among animal handlers, to 3.403% (95% CI 2.44 to 3.932) for farmers, 2.737% (95% CI 0.896 to 8.054) among rangers and hunters, 1.900% (95% CI 0.738 to 4.808) for abattoir workers, and 0.644% (95% CI 0.223-1.849) for healthcare workers, with the lowest estimate found in veterinarians (0.283%, 95% CI 0.040-1.977). Seroprevalence rates for abattoir workers (odds ratio (OR) 4.198, 95% CI 1.060-16.464), animal handlers (OR 2.399, 95% CI 1.318-4.369), and farmers (OR 2.280, 95% CI 1.419 to 3.662) largely exceeded the official notification rates for CCHF in the general population. CCHF is reasonably underreported, and pooled estimates stress the importance of improving the adherence to personal protective equipment use and appropriate preventive habits.

Seroprevalence of Crimean-Congo Hemorrhagic Fever Virus and Rift Valley Fever Virus in human population in Senegal from October to November 2020

Objectives

Rift Valley Fever and Crimean-Congo Hemorrhagic Fever are two infections classified among the emerging diseases to be monitored with highest priority. Studies undertaken in human and animals have shown endemicity of these two arboviruses in several African countries. However, most of the investigations were carried out on domestic cattle and the studies conducted on human populations are either outdated or limited to a small number of well-known endemic areas. It is then critical to better evaluate the burden of these viruses in Senegal at a national scale.

Methods

This work relies on a previous seroprevalence survey undertaken in all regions of Senegal at the end of 2020. The existing biobank was used to determine the immunoglobulin G [IgG] Rift Valley Fever and Crimean-Congo Hemorrhagic Fever seroprevalences by indirect enzyme-linked immunosorbent assay.

Results

The crude seroprevalences of Rift Valley Fever and Crimean-Congo Hemorrhagic Fever were 3.94% and 0.7% respectively, with the northern and central part of the countries as the main exposed areas. However, acute infections reported in both high and low exposed regions suggest sporadic introductions.

Conclusions

This study gives updated information and could be of interest to support the stakeholders in the management of these zoonoses.

Geographical distribution and pathogenesis of ticks and tick-borne viral diseases

Ticks are obligatory hematophagous arthropods that harbor and transmit infectious pathogens to humans and animals. Tick species belonging to Amblyomma, Ixodes, Dermacentor, and Hyalomma genera may transmit certain viruses such as Bourbon virus (BRBV), Dhori virus (DHOV), Powassan virus (POWV), Omsk hemorrhagic fever virus (OHFV), Colorado tick fever virus (CTFV), Crimean-Congo hemorrhagic fever virus (CCHFV), Heartland virus (HRTV), Kyasanur forest disease virus (KFDV), etc. that affect humans and certain wildlife. The tick vectors may become infected through feeding on viraemic hosts before transmitting the pathogen to humans and animals. Therefore, it is vital to understand the eco-epidemiology of tick-borne viruses and their pathogenesis to optimize preventive measures. Thus this review summarizes knowledge on some medically important ticks and tick-borne viruses, including BRBV, POWV, OHFV, CTFV, CCHFV, HRTV, and KFDV. Further, we discuss these viruses' epidemiology, pathogenesis, and disease manifestations during infection.

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.