Crimean-Congo Hemorrhagic Fever Virus Infections in Slaughtered Camels and Abattoir Workers in the United Arab Emirates

Abstract

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease caused by the CCHF virus (CCHFV) and is characterized by the sudden onset of high fever and hemorrhagic manifestations. This study aimed to estimate the seroprevalence of anti-CCHFV antibodies in dromedary camels and workers at the Al Bawadi abattoir in the United Arab Emirates (UAE). In addition, the camels and human subjects were screened for CCHFV RNA, and the knowledge level of abattoir workers regarding CCHF zoonosis was assessed. A cross-sectional study was conducted between March 2022 and June 2023 at the Al-Bawadi abattoir in Al Ain with 393 camels and 86 abattoir workers. Anti-CCHFV immunoglobulin G (IgG) antibody was tested in camel sera using a multispecies indirect enzyme-linked immunosorbent assay (ELISA). The sera of abattoir workers were tested for anti-CCHFV IgG antibody using a human CCHFV ELISA kit. Camel and human serum samples were tested by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) to detect CCHFV RNA. A questionnaire survey was used to evaluate abattoir workers' knowledge of the risk of zoonosis of CCHF. The seroprevalence of anti-CCHFV antibodies in camels slaughtered at the Al-Bawadi Abattoir was 65.1% (95% confidence interval [CI]: 60.4%-70%). However, the RNA prevalence was only 1% (4/393), with cycle threshold (Ct) values ranging from 34.58 to 38.21. The seroprevalence of anti-CCHFV antibodies in abattoir workers was 29.1% (95% CI: 20.3%-40.4%), but none of the abattoir workers tested positive by RT-qPCR. Seropositive abattoir workers had a longer duration of working in the abattoir (median = 10 years; interquartile range [IQR]: 6.0-14.0) than seronegative abattoir workers (median = 7.5 years; IQR: 5.0-14.0) although the difference was not significant (p > 0.05). Most abattoir workers (73%) knew that CCHF is zoonotic. The seroprevalence of anti-CCHFV antibodies was high in both camels and abattoir workers at the Al-Bawadi Abattoir, and viral RNA was detected in four camels. Hence, active surveillance and reinforcement of control measures are recommended.

Keywords: Crimean–Congo hemorrhagic fever; United Arab Emirates; abattoir workers; dromedary camels; molecular detection; seroprevalence.

Figure 1

Map of the study area. The top map shows the location of Al Ain city in the United Arab Emirates, while the bottom map shows the location of the Al Bawadi abattoir in Al Ain city.

Figure 2

The mean sample percentage (S/P% at OD₄₅₀) of anti-CCHFV antibody titer in slaughtered camels at the Al-Bawadi abattoir. The mean percentage (S/P%) at OD₄₅₀ (mean ± SEM) of positive camels with low, medium, and high antibody titer were 69.54 ± 2.16, 115.8 ± 1.04, and 152.3 ± 1.35, respectively.

Figure 3

Mean optical density (OD) of anti-CCHFV antibody in abattoir workers following ELISA for anti-CCHFV at Al-Bawadi abattoir. The means of OD₄₅₀ values (mean ± SEM) of positive abattoir workers with low, medium, and high antibody titer were 0.42 ± 0.032, 1.41 ± 0.10, and 2.46 ± 0.071, respectively.

Figure 4

Detection of Crimean–Congo hemorrhagic fever virus (CCHFV) by reverse transcriptase quantitative real-time polymerase chain reaction (RT-qPCR) in camel sera. The sera of 393 camels were screened for CCHFV by RT-qPCR. Only four camels (Panel (A) ID: 52 and 54, and Panel (B) ID: 331 and 346) were positive. The cycle threshold (Ct) values of the four positive camels ranged from 34.58 to 38.21.

Figure 5

Percentage of abattoir workers reporting zoonotic diseases known to them and the routes of transmission of zoonotic diseases. Brucellosis (77%) and CCHF (73%) were known to the abattoir workers, while blood (70%) and tick bite (49%) were the routes of transmission of zoonotic diseases known by the abattoir workers.