Research in Veterinary Science 75 (2003) 21–25 www.elsevier.com/locate/rvsc
Health status of a population of nutria (Myocastor coypus) living in a protected area in Italy E. Bollo a
a,*
, P. Pregel a, S. Gennero b, E. Pizzoni b, S. Rosati c, P. Nebbia c, B. Biolatti
a
Dipartimento di Patologia Animale, Universit a degli Studi di Torino, Via Leonardo da Vinci, 44, I-10095 Grugliasco (TO), Torino, Italy b Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle dÕAosta, Torino, Italy c Dipartimento di Produzioni Animali, Epidemiologia ed Ecologia, Universit a degli Studi di Torino, Torino, Italy Accepted 31 January 2003
Abstract Ninety trapped nutria (Myocastor coypus) from a protected area of Piedmont (Italy), including the Po river, were examined for the prevalence for lesions in major viscera, selected serum antibodies and enteric bacteria. Coccidial lesions in the liver included cholangitis, calcification and necrosis. Renal lesions were nonsuppurative interstitial nephritis and a single case of renal adenocarcinoma. The lungs had a 41.1% prevalence of nonsuppurative interstitial pneumonia. Ten of 87 sera (11.5%) had antibodies against Leptospira bratislava, 3 of 87 (3.4%) against Leptospira ichterohaemorrhagiae, 15 of 41 (36.6%) against Toxoplasma gondii, and antibodies against encephalomyocarditis virus were detected in 5 of 78 sera (6.4%). All fecal samples were negative for Salmonella, Shigella, and Pseudomonas, and growth of enterobacteriaceae was in the normal range. Ó 2003 Elsevier Science Ltd. All rights reserved. Keywords: Nutria; Myocastor coypus; Pathology; Leptospira; Toxoplasma; Encephalomyocarditis virus
1. Introduction The nutria (Myocastor coypus), a semiaquatic rodent indigenous to South America, has become established throughout Europe (Gosling, 1974; Scaravelli and Martignoni, 1994) and owing to its high reproductive rate and large size, it is causing serious damage to crops, wetland plant communities and drainage networks (Abbas, 1988; Boorman and Fuller, 1981; Ehrlich and Jedynak, 1962; Linscombe et al., 1981; Willner, 1982). In several countries nutria are regarded as a pest, leading to eradication campaigns (Doncaster and Jouventin, 1989; Evans, 1970; Gosling and Baker, 1987; Gosling, 1989). They were first introduced into Italy in 1928 (Lever, 1985) and are now found in most wetlands of northern and central Italy (Cocchi and Riga, 1999; Reggiani et al., 1993). In these areas, nutria are perceived to cause serious damage to agriculture and wetlands (Their burrows damage draining systems in rice-fields and rivers, they devastate of crops
and native plant communities, and compete with native and migrating birds in protected areas.) and this has led to eradication campaigns. Several investigators have provided information on diseases of nutria, with special attention given to agents that might cause epizootics in wild populations, domestic livestock or man (Arcangeli et al., 1997; Howerth et al., 1994; K€ ohler et al., 1987, 1988; Martino and Stanchi, 1998; Menard et al., 2000, 2001; Michel et al., 2001; Soldati et al., 1998; Waitkins et al., 1985; Wanyangu et al., 1986; Wendland et al., 1987). In this paper, we report on lesions in major viscera, the prevalence of antibodies against four disease agents, and fecal bacteria in a population of nutria living in a protected area of Piedmont (Italy), including the Po river. To improve our knowledge of nutria diseases in this area we obtained samples during a population control project.
2. Material and methods *
Corresponding author. Tel.: +39-011-670-9036; fax: +39-011-6709031. E-mail address:
[email protected] (E. Bollo).
Ninety adult nutria were trapped in baited cage traps at Ôclimb-outÕ points in a wetland protected area located
0034-5288/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0034-5288(03)00035-3
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E. Bollo et al. / Research in Veterinary Science 75 (2003) 21–25
around the Po river (Riserva Naturale Garzaia di Valenza, Italy; 45°00ÕN, 08°75ÕE) from February to May 1998 and euthanized with chloroform according to local regulations. The sample included 51 males, 29 females (18 of which were pregnant) and 10 animals whose sex was undetermined. Blood samples were collected immediately after euthanasia by cardiac puncture, sera were separated and frozen, and the animals necropsied. Samples for histological investigations were formalin-fixed, paraffin embedded and 4 lm sections were stained with haematoxylin and eosin. Eighty-seven serum samples were tested for antibodies against Leptospira interrogans serovars bratislava, grippotyphosa, icterohaemorragiae, pomona and tarassovi (micro-agglutinantion test, minimum significant titer: 1:100 final dilution; OIE, 1996), and 15 for Toxoplasma gondii (sero-agglutination test, minimum significant titer:1:8 final dilution). Serum neutralization tests for encephalomyocarditis virus (EMC-V) were carried out on 78 animals in microtiter plates as described by Cardeti et al. (1992, 1993) with minor modifications. Briefly, serum samples, inactivated at 56 °C for 30 min, were diluted twofold in Minimum Essential Medium (Sigma, St. Louis, Missouri, USA) starting at a 1:4 dilution and mixed with an equal volume of EMC-V strain ZRC 276RA/90 (100TCID50 =50 ll) (kindly provided by Dr. Cardeti, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Rome, Italy) for 60 min at 37 °C. Control sera without virus were included in each run to assess toxicity. Subsequently, 100 ll of VERO cells suspension (at the density of 105 cells/ml) (American Type Culture Collection, Manassas, Virginia, USA) were added to each well and plates incubated for 5 days at 37 °C, 5% CO2 , when cytopathic effects were clearly evident in virus-infected control wells.
Fecal samples from 65 animals were examined for major enterobacteria (E. coli, Proteus, Salmonella, Shigella and Pseudomonas) according to published protocols (Power and Mccuen, 1988). Virological investigations for EMC-V were performed on VERO cells according to Amaddeo et al. (1995) using homogenate from the heart, pancreas and brain of two nutria that had antibody titers of 1:8 and 1:64, respectively. Cultures were examined for cytopathic effects after each of the three blind passages.
3. Results The results of the pathological and serological investigations are summarized in Tables 1–4. Thirteen animals had hepatic lesions caused by coccidia, including cholangitis, and fibrosis, necrosis and calcification of hepatic tissue (Table 1; Fig. 1). Coccidia were also seen histologically in the proliferated biliary epithelium in inflamed areas. Eight animals had nonsuppurative interstitial nephritis. These lesions were mostly chronic, multifocal and accompanied by mild to moderate fibrosis. An interesting finding was a discrete, single, irregularly spherical, pale, raised, subcapsular nodule that proved to be a renal adenocarcinoma. Microscopically the tumor was poorly differentiated and characterized by solid nests of cells showing rare mitoses, together with areas of better differentiated adenomatous tissue having a connective tissue matrix and a fibrous capsule. A nonsuppurative interstitial pneumonia was present in 30 animals characterized by patches of consolidation, mainly in the cranial lobes of one or both lungs. Microscopically, the intralobular septa were distended by exudate, and there were areas of desquamation of epi-
Table 1 Lesions in the liver (n ¼ 76), kidney (n ¼ 79) and lung (n ¼ 73) of nutria Males Hepatic coccidiosis Megalocitosis Liver steatosis Vacuolization of hepatic cells Ectasia of hepatic lymph vessels Periportal hepatitis Non suppurative hepatitis Centrilobular hepatic degeneration Non suppurative interstitial nephritis Congenital renal cysts Glomerulonephritis Deposits in BowmanÕs capsule Renal carcinoma Non suppurative interstitial pneumonia Non suppurative bronchitis Suppurative interstitial pneumonia
9 1 1 1
Females
Pregnant females
Sex not determined
Total
Percentage
4
13 2 1 1 1 1 1 1 8 1 1 1 1 30 3 2
17.1 2.6 1.3 1.3 1.3 1.3 1.3 1.3 10.1 1.3 1.3 1.3 1.3 41.1 4.1 2.7
1
1 1 1 1 4 1 1 1 1 14 2
3
3
1
7 1 1
6 1
E. Bollo et al. / Research in Veterinary Science 75 (2003) 21–25 Table 2 Nutria seropositive for Leptospira (n ¼ 87)
L. L. L. L. L.
bratislava grippotyphosa icterohaemorrhagiae pomona tarassovi
No. of examined sera
No. of positive sera
Percentage of positive sera
87 87 87 87 87
10 0 3 0 0
11.5 0 3.4 0 0
Table 3 Antibody titers against T. gondii in nutria (n ¼ 15) Antibody titer
No. of sera
% of sera
1:16 1:32 1:64 1:128 1:256 1:512
1 6 3 3 1 1
6.7 40 20 20 6.7 6.7
Table 4 Antibody titers against EMC-V in nutria (n ¼ 78) Antibody titer
No. of sera
% of sera
1:4 1:8 1:64
2 2 1
2.6 2.6 1.3
thelial cells in bronchi and bronchioli with lymphocyte and plasma cell infiltration. There were also discrete accumulations of polymorphonuclear leucocytes in the lumina of the bronchioli. The lesions differed in severity but were predominantly subacute or chronic. There were three cases of nonsuppurative bronchitis with thickening, hyperemia and catarrhal inflammation of the bronchial mucosa and mucous plugs in the lumina.
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Microscopically, there was a mucous exudate in the lumen of the bronchioles, and the epithelium and lamina propria were infiltrated with leucocytes. Two female nutria had a suppurative interstitial pneumonia with thickening of the alveolar septa by serous or fibrinous exudate, infiltration by polymorphonuclear cells and various degrees of thickening of alveolar walls by connective tissue. Other lung lesions were related to the chloroform-induced euthanasia; they included edema (18 animals), hyperemia (10 animals), haemorrhages (8 animals), emphysema (2 animals) and atelectasis (1 animal). Ten of 87 sera (11.5%) contained antibodies against L. bratislava, while only 3 (3.4%) had antibodies against L. icterohaemorrhagiae. There was no association between the presence of leptospiral antibodies and the presence of renal lesions. Fifteen of 41 sera (36.6%) contained antibodies against T. gondii, most with titers between 1:32 and 1:128. Antibodies against EMC-V were detected in 5 of 78 sera tested (6.4%), with titers ranging between 1:4 and 1:64 (Table 4). All fecal samples were negative for Salmonella, Shigella and Pseudomonas. Growth of enterobacteriaceae was in the normal range. No EMC-V was isolated.
4. Discussion The most relevant findings in the liver were a few parasitic, inflammatory and degenerative lesions. The kidneys showed one adenocarcinoma and a 10.1% prevalence of interstitial nephritis that could have been caused by bacterial infection, poisoning or immunological injury. There were several cases of nonsuppurative pneumonia and two cases of suppurative interstitial pneumonia.
Fig. 1. Nutria liver: irregularly shaped grayish foci induced by coccidia.
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The coccidian parasites in the liver probably belonged to the genus Eimeria; unfortunately we could not identify the species involved. Surveys of Eimeria parasites of nutria have shown that the most important species are E. nutriae, E. myocastori, E. myopotami (E. coypi), E. pellucida, E. seideli, E. fluviatilis and E. obitzwadowski, (Ball and Lewis, 1984; Lewis and Ball, 1984; Pellerdy, 1960; Prasad, 1960). The species present in this population is clearly pathogenic causing significant liver lesions. Further investigations, by examination of feces for oocysts, are needed to identify the species of Eimeria involved, as there are known to be geographical variations in the distribution of species (Ball and Lewis, 1984). An interesting finding is a case of renal adenocarcinoma. Although renal neoplasia is rarely reported in domestic mammals, there are several reports of renal adenoma and adenocarcinoma in feral nutria (Keymer et al., 1999). The etiology of renal tumors is still unclear but genetic factors may play an important part and the founding population of nutria in Europe may have been small (Keymer et al., 1999). Nutria in the population we examined had a relatively high incidence of pneumonia. Pneumonia has been reported before in both farmed and feral nutria and has been related to infection with Streptococcus zooepidemicus (Martino and Stanchi, 1994), Staphylococcus aureus and Pasteurella multocida (Martino and Stanchi, 1994; Stepanenko and Stepanenko, 1977), with prevalence up to 37%. In farmed nutria, cold, high humidity, sudden temperature changes, poor sanitation, overcrowding and the presence of asymptomatic carriers all seem to predispose to disease. Some of these conditions, especially cold and high humidity, could have been responsible for the high prevalence of pneumonia in our sample. Further investigations, including virus isolation, should be performed to better understand the implications of pneumonia in nutria for wildlife, domestic animals and humans. Leptospira was first isolated from the nutria in South America (Anchezar et al., 1949) and it has since been shown that nutria can act as a reservoir for Leptospira even in the absence of clinical or histopathological evidence of infection (Arcangeli et al., 1997; Scaravelli and Martignoni, 2000; Soldati et al., 1998; Twigg and Cuerden, 1966; Waitkins et al., 1985; Wanyangu et al., 1986). Of the nutria we tested, 11.5% had antibodies against L. bratislava, while only 3.4% had them against L. icterohaemorragiae. Because there was no correlation between the presence of antibodies and the presence of renal lesions, it appears that the renal lesions we found are unlikely to have been caused by Leptospira and that infected nutria could act as a source of infection for other species. Toxoplasmosis occurs naturally in both farmed and feral nutria and can be induced experimentally (Holmes
et al., 1977; Howerth et al., 1994; Soldati et al., 1998; Wenzel et al., 1983). Even so the epidemiological relevance of this disease in wild animals is not fully understood. Although about a third of the animals in our sample had low antibody titers against T. gondii, the few animals with high antibody titers did not have typical lesions in target organs and it is thought that the nutria, like other free-living species, could be a potential source of infection for other rodents, canids or humans (Holmes et al., 1977). The fact that of 6.4% of this sample of nutria were seropositive for EMC-V shows that they had contact with the virus even though we were unable to isolate it. To the best of our knowledge, this is the first report of EMC-V seropositive nutria. No seropositive animals were found in a previous investigation even though 25% of the sample were juveniles (Howerth et al., 1994). Although wild animals are known to have a role in the epidemiology of EMC-V disease (Zimmerman et al., 1994), the significance of this virus in nutria has yet to be ascertained. In conclusion, although in the last decades great efforts have been made to establish conservation programs, little attention has been given to the role of infectious diseases in conservation biology, especially with regard to the role of introduced species serving as disease reservoirs. In nutria most pathological investigations have involved farm-raised animals, and there are only a few reports on disease in the wild. Therefore, continuous surveillance for parasitic, bacterial and viral diseases potentially responsible for epizootics in wild animals, in domestic livestock and in humans living in the same habitat are needed.
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