SEROPREVALENCE OF SOME INFECTIOUS DISEASES IN STRAY DOGS IN THE WIDER TERRITORY OF LESKOVAC CITY

Since the last decade, stray dogs have been signifi cant ecological, economical and sociological problem in the world as well as in the Republic of Serbia. Th ey occupy specifi c place in the ecology of big cities and their contact with human population represents danger since they are carriers of many zoonotic infectious diseases. Th e goal of this paper is to present epizootiological survey on some diseases of bacterial, viral and parasitic origin through serological investigation of blood sera and full blood. Th e prevalence of leptospirosis, Tularaemia, West Nile fever and dirofi lariosis has been determined in this research. Th e material included full blood and blood sera of stray dogs in the wider territory of Leskovac city. Th e research methods encompassed standard serological tests: microscopic agglutination test (MAT) for determination of specifi c antibodies against Leptospira spp .; slow and fast agglutination test for determination of antibodies against Tularaemia causative agent ( Francisella tularensis ); agar gel immuno-diff usion (AGID) for detection of specifi c antibodies against West Nile virus –WNV ; modifi ed Knot’s test for the detection of microfi laria. Th e results revealed seropositivity for causative agents of Leptospirosis, Tularaemia


INTRODUCTION
In past decades, the problem of stray dogs is widespread in the territory of the Republic of Serbia. Th e number of stray dogs in cities depends on the size of urban habitat and the number of pet owners, who produce major number of future stray dogs. Considering the fact that stray dogs occupy important place in the ecology of cities because they are reservoirs and vectors of many infectious diseases and that they are commonly in close contact with humans, it is of a great importance to introduce and practice control measures with the aim of disease development prevention (Beck, 1975).
Leptospirosis is one of the most common infectious, zoonotic diseases of many animal species and humans caused by diff erent serovars of spirochetes Leptospira spp. In nature, the organism is maintained in the circle between susceptible species, reservoirs and environment. Th e disease can be found in acute, subacute and chronic form. Tularaemia is a zoonotic infectious disease caused by Gram negative, pleomorphic, immobile, non-sporulating bacteria Francisella tularensis. In nature, Tularaemia aff ects lagomorph species -rabbits, but the disease is confi rmed in more than 100 diff erent domestic and wild animal species, birds, amphibians and reptiles (Ellis et al., 2002). Th e causative agent is relatively resistant in nature and can survive for a long time in water. Natural infections of dogs are rare. Th e dogs can become infected during hunting, by eating infected rodents, through bites or scratches created by contaminated teeth or claws, or with infected ticks (Feldman K.A., 2003). In majority of cases, the disease in dogs is asymptomatic; however, in rare cases there short term anorexia, mild fever, depression, swelling of mandibular lymphatic nodes, myalgia, uveitis and conjunctivitis may occur (Green E. West Nile virus-WNV belongs to the genus Flavivirus, fam. Flaviviridae. It is a member of Japanese encephalitis serogroup. Th e virus is maintained in nature thanks to its circulation between vectors -mosquitoes (Culex spp. and Ae-des spp.) and hosts -birds, horses, humans and other vertebrates (Campbell et al., 2002). West Nile fever can aff ect large number of bird species and mammals. In horses and humans, it causes signifi cant clinical symptoms ranging from fl u-like, mild respiratory syndrome to severe neurological symptoms and death. One of the fi rst serological proofs of WNV circulation in the Republic of Serbia was published in 1972 when the seroprevalence was established in some regions in human population (Bordjoški et al., 1972) Dirofi lariasis is a parasitic disease that has zoonotic character and is caused by Dirofi laria immitis and Dirofi laria repens. Mosquitoes from the genus Aedes, Culex and Anopheles are necessary vectors for spreading of this disease since one part of dirofi laria's living cycle takes place in them. Th e development form of parasite -microfi laria lives in the bloodstream of the host. Most common places for fi nding adult forms are heart cavity for D. immitis, or subcutaneous tissue for D. repens. Dirofi lariosis was primarily disease characteristic for the Mediterranean basin, but, due to the climate changes, it spread out to the north, thus nowadays it can be found in middle Europe (Genchi et al., 2009). Th e fi rst data suggesting the presence of dirofi lariasis in Serbia (ex-Yugoslavia) were published in the 1990s (Dimitrijević S., 1999). Aft erwards, the presence, seroprevalence, diagnostics, therapy and case occurrence were closely monitored in both animals and humans (Genchi et

MATERIAL AND METHOD
Th e study included a total of 50 blood sera samples and 47 samples of full blood. All blood samples were taken from stray dogs that originated from the wider area of Leskovac city.
Blood sera were tested for the presence of antibodies against eight serovars of Leptospira spp.: Icterohaemorrhagiae, Canicola, Pomona, Australis, Grippotyphosa, Bataviae, Sejroe and Bratislava. To determine the presence of specifi c antibodies to the agents of leptospirosis, we used microscopic aggluti-nation test (MAT), which is considered the gold standard.
Th e presence of specifi c antibodies for F. tularensis was determined using fast agglutination method on microscopic slide and slow agglutination method in tubes. Commercial antigen was used (Francisella tularensis antigen, Bioveta, Czech Republic) and method was performed according to manufacturer's instructions.
WNV specifi c antibodies were determined using agar gel immunodiff usion method (AGID) and antigen was prepared as described in the work of Đuričić et al. (Đuričić et al., 2013).
Total of 47 samples of full blood were tested for Dirofi lariasis using modifi ed Knot's test. Th is is fast and reliable method for detection of microfi laria in bloodstream.

RESULTS AND DISCUSSION
Th e results are shown on chart 1.

Chart 1. Seroprevalence of four infectious zoonotic diseases in stray dogs in wider territory of Leskovac city
From the total of 50 tested samples of blood sera, 4 (8%) were tested positive for the presence of specifi c antibodies for Leptospira spp.

CONCLUSION
Considering the fact that dog shelters are one way of solving stray dog problem, the results presented in this paper are important indicator of the presence of infectious zoonotic diseases, which are underestimated in most instances. Leptospirosis is a global problem in veterinary medicine and human health care, and its presence in stray dog population poses danger for other animals and humans (Adler and de la Pena, 2010). Dogs are considered relatively resistant animal species to causative agent of Tularaemia. Still, the presence of seropositive dogs can be good indicator that the causative agent is present in nature in the cycle between tick as vectors, rabbits and other wild animals (Green, 2012). WNV is present in the Republic of Serbia and it circulates in nature, which was identifi ed in epidemics in 2012 and 2013 (Popović et al., 2013), but not in dog population. Th e occurrence and spreading of Dirofi lariosis in the Republic of Serbia is serious problem, which has to be approached from all aspects. It is necessary to establish cooperation between physicians and veterinarians, as well as between sanitary and epidemiological service. Th e raise of awareness is of a great importance.