ISRAEL JOURNAL OF
VETERINARY MEDICINE
A NOTE ON A RETROSPECTIVE STUDY OF
REPRODUCTIVE DISORDERS IN NUTRIA (Myocastor
coypus) DAMS
Vol. 57 (4) 2002
P.E. Martino, N.O. Stanchi, E. Bautusta, D. Arias and M. Gatti
Department of Microbiology- CIC, Veterinary College, University of la
Plata, 60 y 118, CC 296, (1900) La Plata, Argentina
Abstract
A 2-year investigation was undertaken to determine the incidence of reproductive disorders in
primiparous and multiparous nutria in captivity. This report is mostly based on the clinical,
cytological and bacteriological findings in groenland and sapphire dams with a history of
infertility, prenatal and postnatal problems, and vaginal discharge. Infertility and prenatal
problems accounted for the highest incidence with two thirds of the total cases, and in general
their rates were significantly higher (p < 0.01) among primiparous dams than in pluriparous.
Among the infectious causes, significant aerobic bacteria were frequently isolated (76 %) from
vaginal swabs in pure culture, including Escherichia coli, Staphylococcus aureus, Proteus spp,
Klebsiella pneumoniae and beta-hemolytic streptococci (almost all are known as abortigenic
agents in nutria). Cytological lesions, most of which suggested infection, were present in 96 % of
the accessions in which an infectious agent could be identified
Introduction
Besides yielding valuable fur, nutria (Myocastor coypus, Molina 1792) can be a source of
sizeable quantities of highly nutritive and tasty meat.
Fur animals represent a relatively new object of livestock breeding and laboratory
investigations on fur bearing animals are infrequently documented and compared to other domestic
animals. Nutrias are annual polyestrus animals that have cycles every 25-30 days and 2-2.5 deliveries
by year after pregnancies of 127-137 days (1,2). Females are sexually mature at 3-7 months old and
weigh approximately 3.7 kg. Males are active throughout the year. Females which have just delivered
kits, have cycle 1-3 days after parturition. Probably no other phase of nutria ranching presents a more
serious problem to the industry than does reproduction with its decreased profitability and only a few
etiological studies are reported (3). The main purpose of this study is to conduct a retrospective survey
of systematic serological, virological, cytological and bacteriological examinations in nutria with a
history of genital problems to determine whether any single factor is consistently associated with
specific disorders.
Materials and Methods
Rearing and reproductive practices
Management of nutrias is traditional and intensive. Animals are kept in outdoor concrete
cages with indoor pens for whelping and raising of kits. Nutrias are fed a balanced cereal diet mixture
with alfalfa hay that has 1250 kcal/kg metabolizable energy (400 g daily each animal) and have free
access to tap water by means of an automatic system. Feed is served in metallic standard feeders
usually placed on the floor, thereby wastage is minimised. Both sexes are kept together in small
families with the ratio of male-female depending on the scale of production usually around 1:5. Only
males of proven reproductive performance are used. Male fertility is partly based on routine palpation
of the testes and epididymis, and partly on semen quality analysis. Volume, spermatozoa concentration
and motility are studied by sampling the vagina after coitus. Although organized breeding programmes
are not common, farmers prevent indiscriminate mating. Renting males to service dams on other farms
is a way of preventing imbreeding and optimising their potential.
Animals
Ninety-two nutria dams of mostly groenland and sapphire mutations from 2 different
commercial ranches of around 400 breeders in production, were randomly selected among those that
manifested reproductive disorders during the 2-year study. Their mean age was 2.8 + 1.6 years. The
various types of reproductive disorders were grouped in 4 categories:
1. Infertility or failure to conceive (n = 41): barren dams, mated and not confirmed pregnant.
2. Prenatal disorders (n = 19): dams with pregnancy difficulties, loss of pregnancy by
abortions or had stillbirths or prolonged gestation.
3. Postnatal disorders (n = 16) : dystocia or difficult births, death during parturition, decreased
litter size or weak offsprings, agalactia, mastitis and utero-vaginal prolapse.
4. Leucorrhea (n = 14): vulvo-vaginal mucopurulent discharge, vaginitis or pyometra.
Thirty-eight of 92 abnormal nutrias showed more than one of these conditions but they were
categorized according to the major clinical sign. Ten normal sexually mature nutrias (five from each
ranch) were also studied as controls. These animals were selected by their good reproductive
performance and never had health problems. Systematic routine colpocytological investigations were
performed.
Laboratory examinations
Vaginal samples for bacteriological, cytological, mycological and virological examinations
were taken with guarded swabs (Teigland Swabs, Haver Lockhart lab., Shawnee, KS, USA).
The swabs were placed in a transport medium (modified Cary-Blair bacterial transport
medium, Marion Scientific, Kansas City, MO, USA) and cultured within 24 h on blood agar plates
under aerobic and anaerobic conditions. Bacterial species were identified (4,5), and considered to be of
significance when moderate to profuse growth of a single species occurred. Mixed cultures were
interpreted to be of significance only when 1 or 2 of the bacterial species grew profusely and were
dominant. For mycology, examination was limited to direct microscopic observation of lactophenol
cotton blue (0.2%) wet mounts and culturing on tellurite malt agar of the swab sample. Fungal
colonies, if any, were purified and characterized generically on the basis of their colonial and
morphological characters.
Smears from the swabs were prepared for cytology and interpretation was made according to
the following classification: 0 = no polymorphonuclear leukocytes (PMNLs), + = low and moderate
response: up to 25 % PMNLs, and ++ = a major response : > 30% PMNLs.
A virological examination was done using the supernatant of the swab medium, containing
high antibiotic concentrations and served to inoculate golden suckling baby hamsters 4 to 7 days of
age, and lamb kidney cell monolayers.
Taking into account that drinking-water wells could contain nitrates released by agricultural
fertilizers (6), concentrations in water coming from the facilities was toxicologically checked at least
twice during the period by a dip-stick test: Merckoquant 10020 Nitra-test (E.Merck, Darmstadt,
Germany). Two ml of blood was drawn from the femoral vein of unanesthetized individuals and sera
were tested for antibodies against Toxoplasma gondii, Leptospira interrogans serovar canicola ,
serovar icterohemorrhagiae and serovar copenhageni. Antibodies to T.gondii were determined by
indirect hemagglutination (Wample Labs, Cranbury, New Jersey 08512, USA) with titers ≥1:64
considered indicative of infection. Antibodies to the 3 serovars of L.interrogans were investigated with
a modification of the technique described by Cole et al. (7), and titers ≥1:100 were considered
indicative of infection. Specimens which met or exceeded these levels will be referred to as "positive".
The chi square test was performed for statistical analysis, using P < 0.05 as the level of
significance (8).
Results and Discussion
Nutrias in Argentina suffer from a wide range of infectious diseases (9,10) and it is a common
belief that the high rate of reproductive problems is largely attributed to poor housing environment and
nutritional management of the dams, particularly with inexperienced smallholder farmers (11,12). The
breeding history and the incidence of each disorder observed in relation to the laboratory findings are
summarized in Table 1. In general, nutrias with reproductive disorders had lower average litter size
(4.42 kits) than normal nutrias (5.63 kits), according to Kukla (13). Moreover, analysis of breeding
records indicates that between 15 and 20 % of nutrias that are bred fail to produce a live kit. This
failure may be a result of infertility, embryonic loss, early fetal loss, abortion, stillbirth, or perinatal
death (1). Incidence rates of infertility, prenatal and post-natal abnormalities were significantly higher
(p < 0.01) among primiparous dams than in pluriparous, but incidence of vaginal discharge was almost
the same in both groups (p > 0.05). Infertility problems accounted for the most important disorder
among the animals studied affecting almost half of the cases. There was no mortality among nutrias
with problems of infertility, prenatal disorders or vaginal discharge, but 2 dead animals with dystocia
and prolapse of vagina/uterus among the primiparous dams (p < 0.01). Seventy cases (76 %) yielded
significant aerobic bacteriological culture, mostly on primiparous dams ( n = 50) than in multiparous (n
= 20) (p>0.01). Escherichia coli, Staphylococcus aureus and Proteus spp were the most frequently
isolated pathogens from vaginal swabs in pure culture, but were not associated with any specific
disorder. They were followed, in lesser frequency, by Klebsiella pneumoniae, beta-hemolytic
Streptococci, Staphylococcus intermedius, Bacteroides intermedius, Clostridium perfringens and
Pasteurella hemolytica. Three cases of fungal isolation were reported (unidentified filamentous fungi,
Rhizopus spp and Aspergillus niger). Cytological examination of the vagina in domestic animals is
common and shows a wide range of cellular conditions, from absence of lesions to the most severe
changes (14,15). Inflammatory changes associated with bacterial isolation consisted of neutrophilic
infiltration and necrosis, and were of particular value to differentiate bacterial contamination from
infection in this survey. Almost all (97%) of the 70 culture positive cases had a major cytological
response. According to the results of the present investigation, bacterial sampling from the vagina of
abnormal nutria without any clinical signs of genital infection and cytological response could be of low
diagnostic value. The incidence of Proteus was high amongst bacterial reproductive disorder, but its
role is unknown. On the other hand, E.coli, Staphylococcus aureus, Klebsiella and streptococci are
viewed as putative pathogens (9,16) and their isolation should be considered as infections and an
indication for treatment of, aborted nutria, provided the vaginal swab proves positive for corresponding
bacteria. Adenovirus is practically the only viral agent associated with nutrial abortion (17). Virological
investigations on all animals failed to demonstrate a viral cause of any reproductive disorder. Thus,
viruses were probably not a major factor in coypu reproduction in the geographic areas covered by this
survey (10,18). Also, minimal evidence of leptospiral infection was observed serologically: Only ten
animals had a serological reaction, although antibody titers were low and difficult to interpret. Six sera
tested for antibodies to L.interrogans serovar copenhageni were positive at a dilution less than 1:100,
and the 4 other cases had a low incidence of antibodies to Toxoplasma gondii at a dilution of 1:16,
suggesting that although these two agents can be present under farm conditions, their impact on nutrial
infertility remains unclear (19,20). No relevant information came from the control animals studied:
nutrias failed to show clinical signs of disease and their colpocytological samplings revealed a normal
reproductive status according to the standards described (21). The great majority of success diagnoses
made by other authors were of infectious agents (3,22,23). As in this study, most of the accessions were
associated with an infectious bacterial condition. Nutria live in close contact with their environment,
which acts as a constant source of bacteria. Moreover, the bacterial microflora of nutria, like that of the
respiratory tract, consist of common opportunistic pathogens or potentially transient contaminants (24).
Nitrate poisoning has been incriminated as a main cause of low fertility in herbivorous animals (25).
Nitrate concentrations found in this study were always under 25 mg/L, which is an optimun level for
the nutria, which is very susceptible to nitrates (26). However, non-infectious agents, such as
phytoestrogens, endocrine failure, toxicoses, nutritional deficiencies, or other factors not considered or
detected in this study remain to be defined. Heavy losses may occur on ranches unless proper attention
is paid to breeding females during the reproductive period. Conditions such as those described above
may possibly develop as a result of lack of proper care, inadequate feeding, infections of various kinds,
poor housing and general husbandry (2). In field surveys, in which the sample size is limited with a
total of 92 females, there is a risk that some cases may be overlooked.
Disorder
Total cases
(%)
Breeding status
Cytology
Oth
0
NS
S
+
NS
S
++
NS
S
Infertility
41
(44.6)
P*
M**
32
9
10
-
1
1
7
1
2
1
19
1
2
5
2
1
Perinatal
disorders
25
(27.2)
P
M
18
7
1
-
3
2
3
-
10
3
2
1
1
3
Postnatal
disorders
12
(13.0)
P
M
8
4
1
-
1
1
-
-
5
2
2
1
-
Leucorrhea
14
(15.2)
P
M
6
8
-
1
1
1
-
4
5
1
1
1
-
P
M
64
28
1
1
2
3
11
4
5
1
38
15
7
4
92
2
5
15
6
53
11
Subtotal
Total
92
(100)
10
*P - primiparous
S: significant bacteria recovered
**M - multiparous
NS: negative culture or non sisgnificant bacteria
recovered
0, +, ++ : cytological responses
Other - serologically reactive animals. (Details in the
text)
LINKS TO OTHER ARTICLES IN THIS ISSUE
References
1. Scheuring,W.: Diseases of Nutria (Choroby Nutrii), IV Edition, Panstowowe Wydawnictwo
Rolcnize i Lesne (eds.). Warszawa. Poland, 1989.
2. Wenzel, U.: Sumpfbiber, Veb. Deutscher Landwirtschafts Verlag (ed.), Berlin, 1980.
3. Wendland, B., B. Köhler, H. Kühn, and Tornow, U.: Studies in the occurrence of bacterial
infectious diseases in nutria. Arch. Exp. Vet. Med. 41: 420-438, 1987.
4. Lennette, E.H.: Manual of Clinical Microbiology, Lennette et al. eds, Am. Soc. Microbiol.,
Washington DC, 1995.
5. Carter, G., Carter, J.R. (eds): Diagnostic Procedures in Veterinary Bacteriology and
Mycology. 5th Edition, Academic Press, New York, 1990.
6. Seawright, A. A.: Animal health in Australia, Chemical and Plant poisons, Canberra ACT,
Australian Government Publishing Service, 1982.
7. Cole, J. R., Sulzer, C. R. and Pursell, A. R.: Improved microtechnique for leptospiral
microscopic agglutination test. Appl. Microbiol. 25: 976-986, 1973.
8. Snedecor, G. and Cochran, W. G.: Statistical Methods, 6 th edition, Iowa State University.
9. Martino, P. E. and Stanchi, N. O.: Epizootic Pneumonia in nutria. J. Vet. Med. B. 41: 561566, 1994.
10. Martino, P. E. and Stanchi N. O.: Causes of death in captive nutria (Myocastor coypus) in
Argentina. Israel J. Vet. Med., 53: 83-88, 1998.
11.Bura, M., Gluhovschi, N. and Radulescu, V.: Incercári de combatere a infecundit tii
determinate da anestru prelungit la femelele de nutria. Rev. Cresterea Animalelor. 1: 52-55, 1985.
12. Dudaö, A. and Melavc, F.: Ten years of coypu breeding in Yugoslavia. In: Proceedings of
the International Scientific Conference Coypu, Novi Sad, Yugoslavia, pp. 98-104, 1987.
13. Kukla, F.: Reproduction of Coypus breeding in C.S.S.R. In: Proceedings of the
International Scientific Conference Coypu, Novi Sad, Yugoslavia, pp. 60-65, 1987.
14. Darenius, K.: Early foetal death in the mare. Acta Vet. Scand. 33: 147-160, 1992.
15. Bjurström, L.: Aerobic bacteria occurring in the vagina of bitches with reproductive
disorders. Acta Vet. Scand. 34: 29-34, 1993.
16. Mattes, S. 1986. Staphylokokkeninfektionen bei Kaninchen und Pelztieren. Tierärztliche
Umschau. 51,18-23, 1986.
17. Karstad, L. and Budd, J.: A hepatitis-nephritis disease of nutria of probable viral etiology.
Can. Vet. J. 4:81-85, 1963.
18. Albert, G. and Wenzel, U.D.: Nutria keeping and diseases related to way of keeping.
Brühl. 29: 36-38, 1988.
19. Wenzel, U.D. and Keil, H.: Toxoplasmosis in fur bearing animals. In: Proceeding of the
3th Congress Int. Sci. Prod. Anim. Fourrure, Versailles, France. pp. 59-61, 1984.
20. Howerth, E.W., Reeves, A.J., McElveen, M.R. and Austin, F.W.: Survey for selected
diseases in nutria (Myocastor coypus) from Louisiana. J. Wild. Dis. 3: 450-453, 1994.
21. Iudica, C.E. and Alberio, R.H.: Preliminary study of the sexual cycle of the SouthAmerican nutria (Myocastor coypus) by the method of exfoliative colpocytology. Scientifur. 19: 33-42,
1995.
22. Köhler, B., Wendland, B., Winkler, M., Kunter, G., and Horn, G.: Studies into occurrence
of bacterial infectious diseases in coypus (Myocastor coypus, Molina 1782). Arch. Exp. Vet. Med. 42:
877-879, 1988.
23. Körner, E.: Krankheiten bei Sumpfbiber und deren behandlungsmöglichkeiten. Tierärztl.
Prax. 13: 235-240, 1985.
24. Martino, P. E., Stanchi, N. O., Rule, R., Arias, D. and Gatti, M.: Tracheo-bronchial
microflora of nutrias (Myocastor coypus) from two hygienically contrasting farms. Scientifur, 3: 91-98,
2001.
25. Norton, J. H. and Campbell, R. S. F.: Non-infectious causes of bovine abortion. Vet.
Bulletin, 12: 1137-1147, 1990.
26. Wenzel, U. D.: Nitrate and nitrite poisoning in the nutria. In: Proceedings of the
International Scientific Conference Coypu, Novi Sad, Yugoslavia. pp. 71-72, 1987.
1.