Journal of Threatened Taxa | www.threatenedtaxa.org | 26 July
2019 | 11(9): 14220–14223
Is canine distemper virus (CDV) a lurking
threat to large carnivores? A case study from Ranthambhore
landscape in Rajasthan, India
Nadisha Sidhu 1, Jimmy Borah 2, Sunny Shah 3,
Nidhi Rajput 4 & Kajal
Kumar Jadav 5
1,2 WWF-India, Pirojsha
Godrej Building, 172-B, Lodhi Estate, New Delhi 110003, India.
2 Current affiliation: Panthera,
8 West 40 St. F. 18 NY 10018, USA.
3 WWF-India, Western India Tiger Landsacape, Plot #19, 20, Subhash Nagar, Sawai Madhopur, Rajasthan 322001,
India.
4,5 School of Wildlife Forensic and Health, Nanaji Deshmukh Veterinary Science University, Jabalpur, Madhya
Pradesh 482001, India.
1 nadisha.sidhu@gmail.com, 2 jimmyborah@gmail.com (corresponding author), 3 envirosunn@gmail.com,
4 nidhi3rajput@gmail.com, 5 kaju_364@rediffmail.com
doi: https://doi.org/10.11609/jott.4569.11.9.14220-14223
Editor: Aniruddha Belsare, Michigan State University, East Lansing, USA. Date
of publication: 26 July 2019 (online & print)
Manuscript details: #4569 | Received 14 September 2018 | Final received 06
June 2019 | Finally accepted 19 June 2019
Citation: Sidhu, N., J. Borah, S. Shah, N. Rajput & K.K.
Jadav (2019). Is canine distemper virus (CDV) a lurking threat to
large carnivores? A case study from Ranthambhore
landscape in Rajasthan, India. Journal of
Threatened Taxa 11(9): 14220–14223. https://doi.org/10.11609/jott.4569.11.9.14220-14223
Copyright: © Sidhu et al.
2019. Creative Commons Attribution 4.0
International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by adequate credit to the author(s)
and the source of publication.
Funding: WWF-Sweden.
Competing interests: The authors
declare no competing interests.
Acknowledgements:
We would like to acknowledge Mr
Ravi Singh, Secretary General and CEO and Dr Dipankar Ghose,
Director-Species and Landscape, WWF-India for the opportunity and grants to carry
out this research. We would also like to thank Mr
Y.K. Sahu, Field Director, and Mr
Sudarshan Sharma, Divisional Conservator of Forests, Core (I), Ranthambhore Tiger Reserve and District Administration of Sawai-Madhopur for all the support. We are grateful to Dr A.B.
Srivastav, the then Director School of Wildlife Forensic and Health (SWFH) for
the laboratory support. All laboratory work was carried out at the SWFH, Nanaji Deshmukh Veterinary Science University, Jabalpur,
Madhya Pradesh. We would also like to thank VetSERV
India for serum extraction from the blood samples collected. Mr Soumen Dey,
Team Leader-Satpura Maikal
Landscape and his team, along with team at Ranthambhore
and Ms Sailaja Nayak, Project Officer, WWF-India are
thanked for providing necessary support and encouragements.
Abstract: Canine distemper virus (CDV) was reported in wild
tigers from Russia and recently from India.
Very few studies, however, have been carried out to gain an insight into
the prevalence of the disease in India, particularly in the wild. CDV is the etiological agent of one of the
most infectious diseases of domestic dogs.
With the aim of exploring the threat CDV poses for tigers, a preliminary
assessment was carried out to determine its prevalence from villages near Ranthambhore National Park in Rajasthan, India. Free-roaming dog populations within a
4-km-radius of the park’s periphery were tested for antibodies against
CDV. The seroprevalence of CDV antibodies
in the sampled dogs was 86% (95% CI 78–91 %), indicating the probability of the
dogs acting as a reservoir and having been exposed to CDV in the past. The seroprevalence of CAV antibodies was
44.23% (95% CI 35–54 %) and CPV antibodies was 95.19% (95% CI 91–99 %). This could threaten the tiger populations in
the park, considering the close proximity of dogs to tigers. It is, therefore, crucial to assess disease
threats at the domestic-wildlife interface and to establish management
strategies for more effective conservation practices in the landscape.
Keywords: Disease dynamics, free-roaming dogs, Tiger, wildlife
disease management.
The global Tiger Panthera
tigris population faces threats due to various
anthropogenic factors (Karanth & Chellam 2009; Walston et al. 2010; Jhala
et al. 2015; Robinson et al. 2015). The
populations also face new pressures associated with stochastic processes such
as inbreeding depression and disease agents that have the potential to drive
small, isolated populations to extinction (Timm et
al. 2009; Kenney et al. 2014). In recent
times, canine distemper virus (CDV) disease has emerged as one of the most
highly contagious diseases with a fatality rate second only to rabies in canids
(Nagao et al. 2012). The first major
outbreak of CDV disease in large carnivores was reported in 1993 in the
Serengeti, Tanzania, which reduced the lion population by 30% (Roelke-Parker et al. 1996; Nagao et al. 2012). In recent years, CDV has been recognized as a
cause of death in Amur Tigers Panthera tigris altaica with the first
diagnosed fatality from CDV in 2003 (Seimon et
al. 2013). Following this, from 2004 to
2010, more CDV deaths in Amur Tigers were observed causing a significant
decline in tiger numbers at Sikhote Alin (Gilbert et al. 2015).
Recent reports have also confirmed cases of CDV in wild tigers in India
(Guardian 2014). Studies in India looked
at potential mitigation to prevent a spillover of
diseases from dogs to wildlife (Belsare & Gompper 2013, 2015; Belsare et
al. 2014). CDV spillover
in endangered carnivore species is a serious conservation concern. Here we assess CDV antibody prevalence
in free-roaming dog populations around a protected area in western India.
Methods
The study was conducted from July to August 2015 in
the villages located in the peripheral area of the Ranthambhore
National Park (RNP) located between 26.01730N and 76.50260E
in Rajasthan, India. Villages located
within a 4-km-radius of RNP were selected for sampling dogs. Free-roaming dogs found within these villages
are most commonly known to wander into the park.
Dogs were caught with the help of villagers from the
villages that fed and looked after them, and blood was collected via the
cephalic vein using a hand-held syringe.
Three to four dogs were sampled per village across 31 villages (Fig.
1). Blood samples were stored in EDTA
vials at temperatures of 2–5 0C.
A total of 121 samples was collected of which 17 samples were damaged
during the collection and/or during transportation. Plasma was extracted from the remaining 104
samples and stored in a deep freezer maintained at -200C, at the
School of Wildlife Forensic and Health, Nanaji
Deshmukh Veterinary Science University, Jabalpur. The stored samples were analyzed
for IgG antibodies against CDV using the DOT-enzyme linked immune sorbent assay
(ELISA) test (Biogal’s Immunocomb
Canine Vaccicheck Antibody Test Kit; Biogal Galed Labs. Acs Ltd, Israel). A
calibrated colour comb scale provided with the ELISA test kit was used to score
the titer as high, moderate, or low. A high titer of IgG
antibodies against CDV (>1:32 V.N. value) indicated a strong response to the
antigen. The test kit is also designed
to perform the titer test for two other
pathogens—Canine Adenovirus (CAV) and Canine Parvovirus (CPV). Therefore, using the above-mentioned
calibrated colour comb scale, a titer for antibodies
against CAV and CPV was determined as well.
A ≥1:16 V.N. value indicated a high antibody titer
against CAV and similarly a ≥1.80 H.I. value indicated a high antibody titer against CPV.
Results
The seroprevalence of CDV antibodies in the sampled
dogs was found to be 86% (95% CI 78–91 %).
Only 14% of the samples showed negative results. None of the dogs tested had ever been
vaccinated against CDV (pers.comm. district
administration, 2015), suggesting that the dogs had prior natural exposure and
recovery from CDV infection. The fact
that a high percentage of dogs had been exposed to cdv could mean that they could potentially be a reservoir of
the virus and that the dogs in these areas were exposed to the virus through
another infected animal or host. The
seroprevalence of CAV antibodies in the sampled dogs was found to be 44.23%
(95% CI 35–54 %). 46.15% of the samples
tested negative for CAV. The
seroprevalence of CPV antibodies in the sampled dogs was found to be 95.19%
(95% CI 91–99 %). Only 2.88% of the
samples tested negative for CPV.
Discussion
Our study reveals a moderate to high risk of exposure
to CDV for the Tigers as well as the Leopards in RNP. With a population density of 6.4 Tigers per
100km2 (Jhala et al. 2015), the
transmission of the disease pathogen, in case of an outbreak, could be fairly
rapid. A study of CDV infection in the
local dog population surrounding the Serengeti in Tanzania has shown a spillover of CDV from the stray dog population to the lion
population (Viana et al. 2015). Abundant
free-roaming dog populations help expedite a higher contact rate between the
stray dogs, livestock, and the wildlife population (Acosta-Jamett
et al. 2015), which increases the risk of disease transmission and spread. The city of Sawai Madhopur, wherein RNP is situated, and the villages in the
fringe of Ranthambhore is home to about 4,500
stray/feral dogs (Source: District Administration, Sawai
Madhopur). Yoak et al. (2013) have also confirmed the presence of CDV
in the stray dogs found in Sawai Madhopur. CDV antibodies have also been noted in
exposed Wild Boar and deer species (Gilbert et al. 2015). CDV has been evaluated as a possible cause of
disease and extinction risk in different species even outside of the order
Carnivora and has also been demonstrated with serological evidence in a wide
range of families and orders (Gutierrez & Saenz 2016). Further studies, however, will be required to
determine and interpret this risk fully.
Coexistence of susceptible and infected hosts could cause the back and
forth transmission of the virus between multiple hosts, aiding the
disease-causing pathogen to persist within a population or multiple species
populations. This increases the threat
for an endangered population of susceptible hosts such as the Tiger,
particularly when the pathogen has the potential to increase the probability of
extinction in the species (Gilbert et al. 2014).
It is, therefore, important to develop a disease
surveillance strategy early on so as to deal with a probable CDV outbreak. Such a step requires an understanding of
disease dynamics through further research.
It would prove useful to obtain blood samples of live Tigers to test for
the presence of CDV antibodies. For
Tiger deaths reported within the park, it may be important to diagnose the
presence or absence of CDV.
In an ideal situation, it would be preferable to
maintain a smaller village dog population potentially for lower contact rates
between dogs and wildlife and, therefore, fewer spillover
events. Animal birth control (ABC)
programs implemented in and around areas of conservation concern, in
combination with restrictions to the movements of dogs in habitats occupied by
species of conservation concern, might be useful in decreasing spillover events (Belsare & Gompper 2015).
Vaccination of local dog populations alone would
probably be ineffective as a disease control strategy. Most adult dogs in such an environment are
already immune to enzootic pathogens like CDV due to early natural exposure. As such, pup vaccination, rather than adult
dog vaccination, should be evaluated as a potential disease control
intervention (Belsare & Gompper
2015).
It is also suggested that disease control programs
should have a strong component of public outreach (Belsare
& Gompper 2015) and better awareness campaigns in
such conservation concern areas. The
National Tiger Conservation Authority, Government of India, has already issued
a guideline for taking necessary preventive measures in and around protected
areas (NTCA 2014). From a research
perspective, a further epidemiological study should be undertaken to better
understand the dynamics of CDV in natural ecosystems.
RNP, being home to 39 adult tigers, is an important
source population for the species in the western part of India (Bhardwaj 2013; Jhala et al. 2015).
Tigers from Ranthambhore have been
translocated to places like Sariska and Mukundra, where the tiger population were locally
extirpated. Therefore, it is imperative
that such source populations are free from diseases like CDV, the outbreak of
which in the region could cause a loss in the numbers of breeding females,
affecting fecundity and thus causing an overall decline in species
population. Therefore, such a source
population needs to be managed with great efficiency in terms of disease
management.
As human encroachment increasingly restricts the range
of wild carnivores, the interaction between domestic animals and wildlife
continues to rise. In such cases,
urban-domestic species play a central role in the transmission of
pathogens. RNP is situated in a high
human population density area with over 300 villages located in a 5km-radius of
the park (DeFries et al. 2010). There have been reports of Leopards killing
stray dogs in the villages (Appel et al. 1994) which could possibly lead to the
species contracting CDV from infected dog populations. Since Tigers and Leopards have prey resource
overlap along with overlapping territories, CDV infection in Leopards increases
the risk for disease contraction in the Tiger population.
Conclusion
The threat posed by multi-host diseases like CDV
should be considered wherever Tigers coexist and interact with other carnivore
species, as well in areas where villages are present adjacent to tiger
reserves. While it is important to
ensure that there is no spillover of CDV from the local dog population to
Tigers and other wildlife, it is also imperative to maintain a stable
population of such dogs through various means described earlier, so as to
eliminate the risks of potential occurrence and transmission of diseases to the
wild. The anthropogenic pressures in the
form of poaching, retaliatory killings, and dog-transmitted diseases are a
reflection of anthropogenic edge effects that occur in fragmented habitats (Gilbert
et al. 2014). The most viable management
strategy, therefore, would be to maintain Tigers in large and inter-connected
populations that are able to withstand CDV and buffer the effects, should any
outbreak occur. Our findings thus have
important implications, highlighting a need to assess the reservoir dynamics of
CDV to better assess the conservation threats to Tiger populations in the wild.
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