Publikationsdatenbank

Epidemiology of Crimean-Congo haemorrhagic fever virus in ticks and livestock in Balochistan, Pakistan (2020)

Art

Hochschulschrift

Autor

Kasi, Khushal Khan (WE 7)

Quelle

Berlin: Mensch und Buch Verlag Berlin, 2020 — VI, 95 Seiten

ISBN: 978-3-96729-043-1

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/27257

Kontakt

Institut für Mikrobiologie und Tierseuchen

Robert-von-Ostertag-Str. 7-13
14163 Berlin
+49 30 838 51843 / 66949
mikrobiologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne zoonotic disease caused by the arbovirus Crimean-Congo haemorrhagic fever virus (CCHFV). It causes fatal haemorrhagic disease in human. Ticks considered as reservoir and vector for CCHFV. Livestock serve as a transient reservoir for this virus, but do not show clinical signs. In part I (3.2) of this thesis, a cross-sectional study has been conducted from July to September 2016, in which sheep and goats in Balochistan, Pakistan, were examined to determine the CCHFV seroprevalence, spatial distribution of seropositive sheep and goats, and to identify potential risk factors for seropositivity to CCHFV in these animals. To this end, farms and animals selected by systematic sampling, blood samples from 800 sheep and 800 goats collected and information regarding farm management and the kept animals were retrieved using a standard questionnaire. Sera tested for antibodies against CCHFV in two independent ELISA formats and an immunofluorescence assay (IFA) following a hierarchical diagnostic decision tree. By these assays 149 (19%, 95%-CI: 16%-21%) out of 800 sheep serum samples and 37 (5%, 95%-CI: 3%-6%) out of 800 goat serum samples were positive for CCHFV-specific IgG antibodies. Interestingly, at least 8 (5%, 95%-CI: 2%-10%) out of 160 sera pools were from CCHFV viremic sheep, as sera (in pools of 5) tested positive for CCHFV genome by real time PCR (RT-qPCR). Risk factor analysis revealed that the open type of housing (OR=3.76, 95%-CI:1.57-9.56, pvalue=0.003), grazing (OR=4.18, 95%-CI:1.79-10.37, p-value=0.001), presence of vegetation in or around the farm (OR= 3.13, 95%-CI: 1.07-10.15, p-value=0.043), lack of treatment against ticks (OR=3.31, 95%-CI: 1.16-10.21, p-value=0.029), absence of rural poultry (OR=2.93, 95%-CI: 1.41-6.29, p-value=0.004), animals with age > 2 years (OR=4.15, 95%-CI: 2.84-6.19, pvalue<0.001), animals infested with ticks (OR=2.35, 95%-CI: 1.59-3.52, p-value<0.001), and sheep species (OR=4.72, 95%-CI:3.24-6.86, p-value<0.001) represented statistically significant risk factors associated with seropositivity to CCHFV. Taken together this part of study confirms the circulation of CCHFV in livestock in Balochistan, Pakistan. The identification of risk factors might help to reduce the risk of infection in sheep and goats, which may also mitigate the risk for human infection. An interesting option for reducing the risk of CCHFV infection in small ruminants is keeping also chickens, since they pick ticks that transmit CCHFV. In part II (3.3), a cross-sectional study has been conducted from September to November 2017, in the province of Balochistan, Pakistan. Ticks were collected from cattle, sheep and goats in the livestock farms. The ticks were identified morphologically and the result confirmed by genotyping. Further, ticks were analysed to detect CCHFV genome by one-step multiplex real-time RT-qPCR, and positive ticks were sequenced to determine the CCHFV genotype. In 529 livestock infested ticks, 525 (99%) ticks belonged to the genus Hyalomma, and four (1%) ticks were from the genus Rhipicephalus. Within the genus Hyalomma, H. marginatum (n=149; male=92, female=57), H. excavatum (n=135; male=96, female=39), H. dromedarii (n=117; male=101, female=16), H. anatolicum (n=82; male=61, female=21), and H. scupense (n=42; male= 36, female=6) were identified. In the genus Rhipicephalus, R. microplus (n=3), and R. turanicus (n=1) were found. The tick infestations on ruminants were 58 % in sheep (n=307), 28 % in goats (n=146), and 14 % in cattle (n=76). All collected ticks were adults. Four percent (20 out of 525, 95%-CI: 2%-6%) ticks were positive for CCHFV genome (S segment). All CCHFV sequences obtained from the ticks clustered in the Asia-1 genotype. Among the CCHFV-positive ticks, 75% (15 out of 20) were female and 25% (5 out of 20) were male. CCHFV genome was detected most frequently in H. marginatum (30%, 6 out of 20), followed by, H. dromedarii (25%, 5 out of 20), H. excavatum (20%, 4 out of 20), H. anatolicum (20%, 4 out of 20), and H. scupense (5%, 1 out of 20). All CCHFVpositive ticks were found on sheep. The highest number of CCHFV-positive ticks was detected in the Kalat district (60%, 12 out of 20), followed by Quetta (30%, 6 out of 20) and Killa Abdullah (10%, 2 out of 20) districts. This part of the study confirms the circulation of CCHFV in ticks in the south-western part (Balochistan) of Pakistan. It is imperative to take effective tick-control measures in this area, especially to control livestock infestation with ticks, to reduce the risk of CCHF outbreaks in the human population.