|Year : 2016 | Volume
| Issue : 4 | Page : 633-635
Difference in vector ticks dropping rhythm governs the epidemiology of Crimean-Congo haemorrhagic fever & Kyasanur forest disease in India
Devendra T Mourya1, Gajanan N Sapkal1, Pragya D Yadav2
1 Viral Diagnostic Laboratory, National Institute of Virology, Pune 411 001, Maharashtra, India
2 Maximum Containment Laboratory, National Institute of Virology, Pune 411 001, Maharashtra, India
|Date of Submission||15-Feb-2016|
|Date of Web Publication||24-Feb-2017|
Devendra T Mourya
Viral Diagnostic Laboratory, National Institute of Virology, Pune 411 001, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Mourya DT, Sapkal GN, Yadav PD. Difference in vector ticks dropping rhythm governs the epidemiology of Crimean-Congo haemorrhagic fever & Kyasanur forest disease in India. Indian J Med Res 2016;144:633-5
|How to cite this URL:|
Mourya DT, Sapkal GN, Yadav PD. Difference in vector ticks dropping rhythm governs the epidemiology of Crimean-Congo haemorrhagic fever & Kyasanur forest disease in India. Indian J Med Res [serial online] 2016 [cited 2017 Mar 30];144:633-5. Available from: http://www.ijmr.org.in/text.asp?2016/144/4/633/200892
Tick-borne pathogens are present in a large part of the world and cause significant global health concerns. Ticks serve as vector as well as reservoir for several bacterial, rickettsial and viral pathogens within enzootic life cycles. These pathogens have spread and expanded horizons due to agricultural activity and encroachment into unutilized lands thus increasing contacts between humans, domestic and wild animals. The increase in contact with ticks and other ectoparasites has resulted in the emergence of several important zoonotic pathogens including novel viruses .
India has two prominent tick-borne diseases namely, Crimean-Congo haemorrhagic fever (CCHF) and Kyasanur forest disease (KFD),,. Mortality rate of 30-50 per cent was observed associated with different CCHF outbreaks in India. However, morbidity associated with KFD was observed to be 2-20 per cent among different outbreaks ,,,. CCHF is transmitted mainly by tick vector Hyalomma anatolicum, and apart from this by H. marginatum marginatum, H. marginatum rufipes, H. marginatum turanicum and H. marginatum isaaci. KFD is transmitted mainly by Haemaphysalis spinigera; in addition, other Haemaphysalis species such as H. turturis, H. uana kinneari, H. minuta, H. cuspidata, H. bispinosa, H. kyasanurensis, H. wellingtoni and H. aculeate are other known vectors for KFD ,,,,,,,. Both the vector species are widely distributed in all geographical areas of India . KFD is more localized in certain geographical areas, namely, five districts of Karnataka, Chamarajanagar, Nilgiri (Tamil Nadu), Wayanad and Malappuram (Kerala), Pali village (Goa) and recently confirmed in Sindhudurg, Maharashtra State ,, where it occurs in outbreak form, whereas only sporadic cases or import cases of CCHF virus (CCHFV) have been reported from Gujarat, Rajasthan and Uttar Pradesh . Antibody survey in domestic animals has shown a wide prevalence of CCHF throughout the country .
Despite the high potential of virus transmission by these vector ticks that are distributed throughout the country, the incidences of these viruses are compartmentalized or restricted in geographic locations. Here, we report the behaviour of tick's dropping rhythm that governs the epidemiology of CCHF and KFD in India. Ticks of the genus Haemaphysalis and Hyalomma serve as vector as well as reservoir for KFD virus (KFDV) and CCHFV, respectively ,,,,.
Numerous wild animals, birds and livestock serve as amplifying hosts for these viruses ,,. Transmission to humans occurs through bites of infected ticks or unprotected contact with infected animal/human. Human-to-human spread of CCHF cases occurs due to unprotected contact with infectious blood or body fluids. While human acquires KFD infection by the bites of infected H. spinigera, there is no evidence of human-to-human transmission.
Both KFD and CCHF vectors are two-host ticks and require two hosts to complete their life cycles. The adults lay eggs and emerging larvae attach to the vertebrate host. Hyalomma anatolicum parasitizes mainly cattle. The detachment and dropping rhythms of the species are so adjusted that these occur only at a time when the cattle is resting in the sheds normally at night time. The engorged ticks that drop in the sheds find suitable niche in the cracks and the crevices, where the female ticks oviposit and the larvae and the nymph moult to the next stage. The questing larvae, the unfed nymphs and adults that have moulted from the previous stage can easily find their hosts in the cattle sheds. The humans acquire infection when they come in close contact of this environment. Therefore, only sporadic cases occur for CCHF though the virus is widely prevalent in various geographical areas.
The KFD incidences occur in persons entering the endemic forest areas, particularly the hotspots as the dropping of Haemaphysalis spp. ticks occur anywhere the animals move while grazing. Fed female ticks lay eggs, which hatch to larvae under the foliage. They further drop on vertebrates, particularly small mammals and feed on them. Subsequently, they mature to nymphs and drop from the host body. By this time, the attached larvae have moved to various distances travelling on the body of small mammals, generating larger focus of infected spots . The nymphs climb to nearby shrubs and rest at the apex of leaves [Figure 1] and wait in search of vertebrate host . As a result, monkeys and forest dwellers acquire KFD infections. On the contrary, CCHF vector Hyalomma spp. remains confined to resting shades of the animals  and accidental bites occur to human residing in close proximity to the animals, thus only sporadic cases occur.
KFDV is transmitted to the wild monkeys; the black-faced langur (Presbytis entellus) and the red-faced bonnet monkey (Macaca radiata) through bites of infected H. spinigera ticks. These are very susceptible animals like humans and succumb to the infections. Once death of animal occurs, the attached nymphs leave the body and spread around in search of a new host. This creates a hotspot of infection in the forest .
There are several differences in the bionomics of the two vector tick species, but this single behavioural difference of dropping rhythm governs the epidemiology of these two tick-borne diseases, namely, KFD and CCHF in India.
Understanding vectors and their bionomics must be taken on priority so that better interventions can be made to control such zoonotic infections. Increasing awareness among rural population and change in their behaviour for keeping animal sheds away from houses and taking anti-tick precautions would help in reducing the incidences of these diseases.
Conflicts of Interest: None.
| References|| |
Ghosh S, Nagar G. Problem of ticks and tick-borne diseases in India with special emphasis on progress in tick control research: a review. J Vector Borne Dis
Mourya DT, Yadav PD, Patil DY. Highly infectious Tick-borne viral diseases: Kyasanur forest disease and Crimean-Congo hemorrhagic fever in India. WHO South East Asia J Public Health
Mourya DT, Yadav PD. Recent scenario of emergence of Kyasanur forest disease in India and public health importance. Curr Trop Med Rep
Mourya DT, Yadav PD, Shete AM, Gurav YK, Raut CG, Jadi RS, et al.
Detection, isolation and confirmation of Crimean-Congo hemorrhagic fever virus in human, ticks and animals in Ahmadabad, India, 2010-2011. PLoS Negl Trop Dis
Mourya DT, Yadav PD, Shete AM, Sathe PS, Sarkale PC, Pattnaik B, et al.
Cross-sectional serosurvey of Crimean-Congo hemorrhagic fever virus IgG in livestock, India, 2013-2014. Emerg Infect Dis
Ergönül O. Crimean-Congo haemorrhagic fever. Lancet Infect Dis
Singh KR, Pavri KM, Anderson CR. Transmission of Kyasanur forest disease virus by Haemaphysalis turturis
, Haemaphysalis papuana
kinneari and Haemaphysalis minuta
. Indian J Med Res
Bhat HR, Sreenivasan MA, Goverdhan MK, Naik SV. Transmission of Kyasanur forest disease virus by Haemaphysalis kyasanurensis
trapido, Hoogstraal and Rajagopalan, 1964 (Acarina: Ixodidae
). Indian J Med Res
Singh KR, Bhatt PN. Transmission of Kyasanur forest disease virus by Hyalomma marginatum
isaaci. Indian J Med Res
Boshell J, Rajagopalan PK, Patil AP, Pavri KM. Isolation of Kyasanur forest disease virus from ixodid ticks: 1961-1964. Indian J Med Res
Singh KR, Goverdhan MK, Bhat UK. Transmission of Kyasanur forest disease virus by soft tick, Argas persicus
). Indian J Med Res
Bhat UK, Goverdhan MK. Transmission of Kyasanur forest disease virus by the soft tick, Ornithodoros crossi
. Acta Virol
Awate P, Yadav P, Patil D, Shete A, Kumar V, Kore P, et al.
Outbreak of Kyasanur forest disease (monkey fever) in Sindhudurg, Maharashtra State, India, 2016. J Infect
Yadav PD, Raut CG, Patil DY, Majumdar TD, Mourya DT. Crimean-Congo hemorrhagic fever: current scenario in India. Proc Natl Acad Sci India Sect B Biol Sci
Banerjee K. Kyasanur forest disease. In: Monath TP, editor. Arboviruses
. Boca Raton (FL): CRC Press; 1990. p. 93-116.
Pattnaik P. Kyasanur forest disease: an epidemiological view in India. Rev Med Virol
Whitehouse CA. Crimean-Congo hemorrhagic fever. Antiviral Res
Geevarghese G, Mishra AC. Haemaphysalis ticks of India. 1st ed. London: Elsevier; 2011.
Geevarghese G, Dhanda V. The Indian Hyalomma
ticks (Ixodoidea: Ixodidae
). New Delhi, India: Indian Council of Agricultural Research; 1987. p. 119.
Mourya DT, Yadav PD, Sandhya VK, Reddy S. Spread of Kyasanur forest disease, Bandipur Tiger Reserve, India, 2012-2013. Emerg Infect Dis