ISSN 1063-0740, Russian Journal of Marine Biology, 2009, Vol. 35, No. 6, pp. 494–497. © Pleiades Publishing, Ltd., 2009. Original Russian Text © A.Yu. Alekseev, A.Yu. Reguzova, E.I. Rozanovab, A.V. Abramov, Yu.V. Tumanov, I.N. Kuvshinova, A.M. Shestopalov, 2009, published in Biologiya Morya.
ECOLOGY
Detection of Specific Antibodies to Morbilliviruses, Brucella and Toxoplasma in the Black Sea Dolphin Tursiops truncatus ponticus and the Beluga Whale Delphinapterus leucas from the Sea of Okhotsk in 2002−2007 A. Yu. Alekseeva, A. Yu. Reguzovaa, E. I. Rozanovab, A. V. Abramovb, Yu. V. Tumanova, I. N. Kuvshinovac, and A. M. Shestopalova a
Vector State Research Center of Virology and Biotechnology, Rospotrebnadzor, Koltsovo, Novosibirsk oblast, 630559 Russia b Utrishskiy Dolphinarium, Moscow, 119071 Russia c Vector-Best Koltsovo, Novosibirsk oblast, 630559 Russia e-mail:
[email protected] Received March 26, 2009
Abstract—The prevalence of antibodies to morbilliviruses, Brucella and Toxoplasma was studied in the Black Sea bottlenose dolphin Tursiops truncatus ponticus and the beluga whale Delphinapterus leucas from the Sea of Okhotsk. The blood serum of 74 dolphins and 147 beluga whales was tested in 2002–2007. Antibodies to morbilliviruses were detected in 15 (20.3%) bottlenose dolphins and 20 (13.6%) beluga whales. Antibodies to Brucella were detected in 17 (23.0%) bottlenose dolphins and 10 (6.8%) beluga whales. Toxoplasma-specific antibodies were detected in 39 (52.7%) bottlenose dolphins and 7 (4.8%) beluga whales. Some animals had antibodies to two, or even three, of the pathogens. A high level of incidence of the pathogens in the sea animals was found in the densely populated coastal areas with high economic development. Key words: Bottlenose dolphin, beluga whale, antibodies, morbilliviruses, Toxoplasma, Brucella. DOI: 10.1134/S1063074009060078
The Black Sea bottlenose dolphin Tursiops truncatus ponticus Barabasch–Nikiforov, 1940 (Russ. “afalina”) is common in the temperate and warm waters of the World Ocean. This species leads a settled mode of life or roves in pods, mainly in the near-shore zone, which is explained by its near-bottom feeding. The protection status of the bottlenose dolphin in Russia and the Ukraine is Category III, which is defined as “a rare endemic subspecies.” The Black Sea population of the dolphin T. truncatus ponticus was put in the Classification of “Endangered” within The Global Plan of Action for the Conservation, Management, and Utilization of Marine Mammals, which is a UNEP’s leading document. The beluga whale Delphinapterus leucas Pallas, 1776 or a white polar dolphin is circumpolar and lives among the icebergs and floating ice-floes of the Arctic. Unlike the bottlenose dolphin that occurs in inshore marine waters, the beluga whale is common in open waters of the northern seas. This species is highly social and lives in pods of 70–90 individuals. In recent years, cases of new infectious diseases in marine mammals have increased. Sometimes, large outbreaks of these diseases—epizootics—lead to the
death of animal populations. However, the carrying of infections by the Black Sea bottlenose dolphin and beluga whale and the background of antibodies to specific pathogens have been studied little if at all. At the same time, an increasing body of evidence suggests that outbreaks of infectious diseases in wild-animal populations are associated with human activities [5]. The anthropogenic effect on the environment can manifest itself as the transmission or introduction of infectious agents and their hosts into new ecological niches and as the general influence of radiation, chemical and other kinds of environmental contamination on the host organism. An increasing number of reports on reduced natural resistance to bacterial and viral infections in marine mammals experiencing the effects of high concentrations of anthropogenic pollutants, e.g., organic halogens, have been published [6, 19, 23]. The area of geographical distribution of the Black Sea bottlenose dolphin is the Black Sea and the Azov Sea. These seas are surrounded by densely populated territories, which have long been utilized by humans and are now a zone of vigorous human activities. The indices that characterize the state of the socio–ecological–economic system in this region are as follows: the
494
DETECTION OF SPECIFIC ANTIBODIES TO MORBILLIVIRUSES
495
Table 1. The seroprevalence of antibodies to infectious agents in the Black Sea bottlenose dolphins Year of sampling Number of animals 2003 2004 2005 2006 2007 Total
17 21 19 9 8 74
Pathogen brucella
morbillivirus
Lack of antibodies to pathogens
2(11.7 ± 7.8%) 11(52.3 ± 10.9%) 3(25.0 ± 9.9%) 1(11.1 ± 0.5%) 0(0%) 17(23.0 ± 4.9%)
1(5.8 ± 5.7%) 9(42.8 ± 10.8%) 2(16.7 ± 8.5%) 2(22.2 ± 13.9%) 1(12.5 ± 11.7%) 15(20.3 ± 4.7%)
14(82.3 ± 9.2%) 1(4.7 ± 4.6%) 6(50.0 ± 11.5%) 3(33.3 ± 15.7%) 3(37.5 ± 17.1%) 27(36.5 ± 5.6%)
toxoplasma 0(0%)* 18(85.7 ± 7.6%) 11(91.7 ± 6.3%) 6(66.6 ± 5.7%) 4(50.0 ± 7.7%) 39(52.7 ± 5.8%)
* Number of sea animals (percent ± error of mean).
intensity of anthropogenic effects on the environment is 20–40; the intensity of use of total natural resources is 20 (www.sci.aha.ru/RUS/mapind.htm); and anthropogenic load on the Black Sea coastal zone is (www.biodat.ru/doc/lib/agro04. >100 humans/km2 htm). The Sea of Okhotsk—one of the areas where the beluga whale occurs—communicates with the Pacific Ocean; its neighboring territories have sparse human population. The intensity of use of total natural resources is 3–6; the intensity of the anthropogenic effect on the environment is about 20 (www. sci.aha.ru/RUS/mapind.htm); anthropogenic load on the territory is 1–3.5 humans/km2 (www.biodat. ru/doc/lib/agro04.htm). The literature data on pathogens circulating among marine mammals suggest that morbilliviruses, Brucella spp., and Toxoplasma are the most dangerous pathogens to humans and agricultural animals. Outbreaks of morbilliviral infections causing epizootics with mass mortalities are very likely to occur in highly social bottlenose dolphin and beluga whale [12, 13]. Apart from the viruses, bacterial and parasitic diseases can have a prolonged effect on the numbers of animal populations. Brucellosis and toxoplasmosis are such infections. The chronic character of the diseases leads to weakening of immunity and indirectly affects the abundance of the animal population. The damage to a fetus inflicted by the disease can cause its abortion or the birth of nonviable progeny [16]. Brucellas can be transferred to humans. Cases of human brucellosis infection from marine mammals have been reported (www.cfsph.iastate.edu). The protozoic parasite Toxoplasma gondii and antibodies to it have been found in a large number of marine mammals [8, 14, 15]. Regular monitoring of the circulation of pathogens in bottlenose dolphin and beluga whale populations is of great importance because of the possibility of transfer of the above infections to humans in contact with marine mammals and because of the need to preserve the abundance of these unique animals. Furthermore, it would be of interest to compare the infection level in RUSSIAN JOURNAL OF MARINE BIOLOGY
Vol. 35
sea animals living in areas with different anthropogenic loads. The purpose of this work was to carry out monitoring of morbilliviral, brucellosis, and toxoplasmosis infections in bottlenose dolphins in the Black Sea and beluga whales in the Sea of Okhostk. MATERIAL AND METHODS Material from 74 Black Sea bottlenose dolphins was collected in 2003–2007 in Taman Bay in the Black Sea. Blood samples from the caudal fin vessels were taken into vacuum tubes, maintained until a serum layer was formed, and centrifuged for 15 minutes at 3000– 3200 rpm. After separation, plasma or serum was placed in polyethylene tubes and frozen at –20°C. Material from 147 beluga whales was collected in 2002–2007 at Chkalov Island (Amur Liman, Sea of Okhotsk). Blood samples from the caudal fin vessels were taken as described above. Antibodies (the sum of IgG and IgM) to brucellas, morbilliviruses, and toxoplasma were detected using the immune enzyme assay according to the previously described procedure [1]. Statistical processing was carried out using standard methods [2]. RESULTS AND DISCUSSION This study revealed the prevalence of antibodies to morbilliviruses, brucella, and toxoplasma in the Black Sea bottlenose dolphin and beluga whale from the Sea of Okhotsk. Morbillivirus-specific antibodies were detected in 15 (20.3%) bottlenose dolphins and 20 (13.6%) beluga whales. The numbers of bottlenose dolphins and beluga whales that were serum-positive to brucellas were 17 (23.0%) and 10 (6.8%), respectively. Toxoplasma-specific antibodies were found in the serum of 39 (52.7%) bottlenose dolphins and 7 (4.7%) beluga whales (Tables 1, 2). The simultaneous occurrence of antibodies to two or three pathogens in the blood of one animal was serologically confirmed. Thus, antibodies to brucella occurred together with antibodies to morbilliviruses in the blood No. 6
2009
496
ALEKSEEV et al.
Table 2. The seroprevalence of antibodies to infectious agents in beluga whales from the Sea of Okhotsk Year of sampling
Number of animals
2002 2003 2004 2005 2006 2007 Total
2 33 7 4 31 70 147
Pathogen toxoplasma
brucella
0(0%)* 1(3.0 ± 2.9%) 1(14.3 ± 13.2%) 0(0%) 2(6.4 ± 4.4%) 3(4.2 ± 1.7%) 7(4.7 ± 1.7%)
2(100%) 5(15.1 ± 6.2%) 1(14.3 ± 13.2%) 1(25.0 ± 21.6%) 0(0%) 1(1.4 ± 1.4%) 10(6.8 ± 2.1%)
morbillivirus
Lack of antibodies to pathogens
0(0%) 0(0%) 5(15.1 ± 6.2%) 22(66.6 ± 8.2%) 1(14.3 ± 13.2%) 4(57.1 ± 18.7%) 1(25.0 ± 21.6%) 2(50.0 ± 25.0%) 2(6.4 ± 4.4%) 27(87.1 ± 6.0%) 11(15.7 ± 4.3%) 55(78.6 ± 4.9%) 20(13.6 ± 2.8%) 110(74.8 ± 3.6%)
* Number of sea animals (percent ± error of mean).
serum of three beluga whales. Among the bottlenose dolphins, seven specimens in 2004 and two in 2005 had antibodies to both toxoplasma and brucella. The simultaneous presence of antibodies to toxoplasma and morbilliviruses was found in three bottlenose dolphins in 2004 and in one in 2006. Antibodies to the three pathogens were detected in four bottlenose dolphins in 2004 and in one bottlenose dolphin in 2006. Morbillivirus-specific antibodies were found in approximately the same number of bottlenose dolphins and beluga whales (P < 0.05). The dynamics of carrying of antibodies to morbilliviruses did not change markedly during the period of this study. The morbilliviruses are known to infect many species of mammals, not necessarily producing apparent symptoms of the disease [21]. However, the presence of antibodies can be indicative of the chronic form of the infection. The chronic course of the disease negatively affects the animals, decreasing their immunity indices and leading to abortions, still births, and high mortalities in both juveniles and adults [9]. The data [9, 10, 16] show that the agents of brucellosis have been isolated from dolphins in various regions of the world. Our investigations also suggest the presence of antibodies to brucellas in beluga whales and bottlenose dolphins living in geographically setapart regions. In 2002–2007, we found antibodies to bacteria of the genus Brucella in 10 out of 147 (6.8%) of the investigated beluga whales from the Sea of Okhotsk. The Black Sea bottlenose dolphins that were seropositive to this agent were almost three times as great (P < 0.05). Brucellas are widespread among marine animals, and they have probably been long endemic to these populations. The transmission of brucellas in marine mammals has been studied poorly. Most species of Brucella are initially associated with a particular host; however, other animal species in close contact can also be infected by them. The situation is aggravated by the fact that several infections may present that have a clinical picture similar to that of brucellosis. A number of diseases lead to abortions, the death of newly born animals, meningoencephalitis, and
inflammations. Brucellosis can proceed without symptoms and can only be revealed from positive results of serological tests. The present study, using the immune enzyme assay, has shown the prevalence of antibodies to Toxoplasma gondii in wild beluga whales from the Sea of Okhotsk and bottlenose dolphins from the Black Sea. Our results are consistent with the data on cetaceans inhabiting other regions [4, 7, 18]. The presence of toxoplasma in beluga whales was confirmed by the detection of antibodies in 7 (4.7%) out of the 147 samples collected in 2002–2007. Toxoplasma-specific antibodies were found in the blood serum of 39 (52.7%) bottlenose dolphins examined during the period of 2003–2007. The presence of toxoplasma in the marine mammals provides an ecological indicator of contamination of marine and coastal waters with the oocysts of the given protozoan parasite [11, 20]. Some investigators believe that surface water runoff containing feline excrement leads to the contamination of fresh water and the marine environment with T. gondii oocysts, thus producing a risk of infection of sea animals [3, 17]. The Sea of Okhotsk is bordered by sparsely populated land areas and therefore receive runoff that is less contaminated with the oocysts of this parasite. Accordingly, the average incidence of antibodies here was 4.7%. This value is markedly lower compared to that in the Black Sea, where the antibodies to toxoplasma were present in 52.7% of bottlenose dolphins (P < 0.05). There is a risk of human infection with toxoplasma due to the use of oocyst-contaminated water or the eating of raw or undercooked meat infected with T. gondii, which is considered to be the main route of the pathogen’s transfer to humans [22]. This is particularly the case for the indigenous people of the extreme North, who carry out the fishery for marine mammals. Thus, we presented the serological evidence for the circulation of toxoplasma, brucella, and morbilliviruses in bottlenose dolphins from the Black Sea and in beluga whales from the Sea of Okhotsk. A high incidence of the pathogens in these sea animals was found in the densely populated coastal areas with high economic
RUSSIAN JOURNAL OF MARINE BIOLOGY
Vol. 35
No. 6
2009
DETECTION OF SPECIFIC ANTIBODIES TO MORBILLIVIRUSES
497
development. The highest occurrence of antibodies to the tested pathogens and the persistence of their dynamics was observed in bottlenose dolphins from the Black Sea. The ecological situation in the remote regions of the North is better. The results from this study provide further evidence supporting the adverse effects of anthropogenic environmental changes on the abundance and health of marine animals.
10. Jahans, K.L., Foster, G., and Broughton, E.S., The Characteristics of Brucella Strains Isolated from Marine Mammals, Vet. Microbiol., 1997, vol. 57, pp. 373–382.
REFERENCES
13. Kennedy, S., Kuiken, T., and Jepson, P.D., Mass Die-off of Caspian Seals Caused by Canine Distemper Virus, Emerg. Infect. Dis., 2000, vol. 6, pp. 637–639.
1. Alekseev, A.Yu., Rozanova, E.I., Ustinova, E.N., et al., Antibodies to Morbilliviruses, Brucella and Toxoplasma in the Captive Bottlenose Dolphin Tursiops truncatus ponticus from the Black Sea, Biol. Morya, 2007, vol. 33, no. 6, pp. 465–468. 2. Usovich, A.T. and Lebedev, P.T., Primenenie matematicheskoi statistiki pri obrabotke eksperimental’nykh dannykh v veterenarii (Application of Mathematical Statistics to Experimental Data Treatment in Veterinary), Omsk: Zapadnosibirskoe Knizhn. Izd. (West Siberian Book Publishers). 1970. 3. Bandoli, J.G. and de Oliveira, C.A.B., Toxoplasmose em Sotalia guianensis (Van Beneden, 1863) Cetacea-Delphinidae, Folha Méd., 1977, vol. 75, pp. 459–468. 4. Cabezon O., Resendes A.R., Domingo M. et al. Seroprevalence of Toxoplasma gondii Antibodies in Wild Dolphins from the Spanish Mediterranean Coast, J. Parasitol., 2004, vol. 90, pp. 643–644. 5. Daszak, P., Cunningham, A.A., and Hyatt, A.D., Anthropogenic Environmental Change and the Emergence of Infectious Diseases in Wildlife, Acta Trop., 2001, vol. 78, no. 2, pp. 103–116. 6. De Guise, S., Lagacé, A., Béland, P., et al., Non-neoplastic Lesions in Beluga Whales (Delphinapterus leucas) and Other Marine Mammals rom the St. Lawrence Estuary, J. Comp. Pathol., 1995, vol. 112, pp. 257–271. 7. Dubey, J.R., Fair, P.A., Bossartt, G.D., et al., A Comparison of Several Serologic Tests to Detect Antibodies to Toxoplasma gondii in Naturally Exposed Bottlenose Dolphins (Tursiops truncatus), J. Parasitol., 2005, vol. 5, no. 91, pp. 1074–1081. 8. Dubey, J.P., Zarnker, R., Thomas, N.J., et al., Toxoplasma gondii, Neospora caninum, Sarcocystis neurona, and Sarcocystis canis-Like Infections in Marine Mammals, Vet. Parasitol., 2003, vol. 116, pp. 275–296. 9. Foster, G., Jahans, K.L., Reid, R.J., and Ross, H.M., Isolation of Brucella Species from Cetaceans, Seals and an Otter, Vet. Rec., 1996, vol. 138, pp. 583–586.
RUSSIAN JOURNAL OF MARINE BIOLOGY
Vol. 35
11. Jardine, J.E. and Dubey, J.P., Congenital Toxoplasmosis in a Indo-Pacific Bottlenose Dolphin (Tursiops aduncus), J. Parasitol., 2002, vol. 88, pp. 197–199. 12. Jensen, T., van de Bildt, M., and Dietz, H.H., Another Phocine Distemper Outbreak in Europe, Science, 2002, vol. 297, p. 209.
14. Lambourn, D.M., Jeffries, S.J., and Dubey, J.P., Seroprevalence of Toxoplasma gondii in Harbor Seals (Phoca vitulina) in Southern Puget Sound, Washington, J. Parasitol., 2001,vol. 87, no. 5, pp. 1196–1197. 15. Mikaelian, I., Boisclair, J., Dubey, J.P., et al., Toxoplasmosis in Beluga Whales (Delphinapterus leucas) from the St. Lawrence Estuary: Two Case Reports and a Serological Survey, J. Comp. Pathol., 2000, vol. 122, pp. 73– 76. 16. Miller, W.G., Adams, L.G., Ficht, T.A., et al. BrucellaInduced Abortions and Infection in Bottlenose Dolphins (Tursiops truncatus), J. Zoo Wildl. Med., 1999, vol. 30, pp. 100–110. 17. Miller, M.A., Gardner, I.A., Kreuder, C., et al., Coastal Freshwater Runoff Is a Risk Factor for Toxoplasma gondii Infection of Southern Sea Otters (Enhydra lutris nereis), Int. J. Parasitol., 2002, vol. 32, pp. 997–1006. 18. Murata, K., Mizuta, K., Imazu, K., et al., The Prevalence of Toxoplasma gondii Antibodies in Wild and Captive Cetaceans from Japan, J. Parasitol., 2004, vol. 4, no. 90, pp. 896–898. 19. Parsons, E.C.M. and Jefferson, T.A., Post-mortem Investigations on Stranded Dolphins and Porpoises from Hong Kong Waters, J. Wildl. Dis., 2000, vol. 36, pp. 342–356. 20. Ratcliffe, H.L. and Worth, C.B., Toxoplasmosis of Captive Wild Birds and Mammals, Am. J. Pathol., 1951, vol. 27, pp. 655–667. 21. Reidarson, T., McBain, J., House, C., et al., Morbillivirus Infection in Stranded Common Dolphins from the Pacific Ocean, J. Wildl. Dis., 1998, vol. 34, pp. 771–776. 22. Tenter, A.M., Heckeroth, A.R., and Weiss, L.M., Toxoplasma gondii: From Animals to Humans, Int. J. Parasitol., 2000, vol. 30, pp. 1217–1258. 23. Thompson, H.G., Hall, J.G., Lee, W.E., et al., Rapid Immunofiltration Assay of Newcastle Disease Virus Using a Silicon Sensor, J. Immunol. Meth., 1993, vol. 166, no. 1, pp. 123–131.
No. 6
2009
