Tick-Borne Zoonotic Bacteria in Wild and Domestic Small Mammals in Northern Spain

The prevalence and diversity of tick-borne zoonotic bacteria (Borrelia spp., Anaplasma phagocytophilum, Coxiella burnetii, and spotted fever group rickettsiae) infecting 253 small mammals captured in the Basque Country (Spain) were assessed using PCR and reverse line blot hybridization. Trapping sites were selected around sheep farms (study 1, 2000 to 2002) and recreational parks (study 2, 2003 to 2005). The majority of the studied mammals (162) were wood mice (Apodemus sylvaticus), but six other different species were also analyzed: yellow-necked mice (Apodemus flavicollis), shrews (Crocidura russula and Sorex coronatus), bank voles (Clethrionomys glareolus), domestic mice (Mus domesticus), and moles (Talpa europaea). The results showed an infection rate ranging from 10.7% to 68.8%, depending on the small mammal species. One C. russula shrew and one A. sylvaticus mouse gave positive reactions for A. phagocytophilum, and C. burnetii was detected in two domestic mice and one A. sylvaticus mouse in a farm. The DNA of Borrelia spp. was detected in 67 animals (26.5%), most of them presenting positive hybridization with the probe for Borrelia sp. strain R57, the new Borrelia species previously detected in small mammals in our region. Furthermore, a second PCR and reverse line blot hybridization specific for B. burgdorferi sensu lato revealed the presence of Borrelia afzelii in 6.3% of C. glareolus voles and 14.3% of S. coronatus shrews. All small mammals were negative for spotted fever group rickettsiae. These results highlight the relevance of small mammals as reservoirs of some zoonotic bacteria.     

Small mammal populations in relation to hedgerow structure in an arable landscape

The population ecology of small mammals in hedgerows in arable farmland in eastern England is described. Features of hedgerows of importance to individual species are examined. Some 97% of the total 3042 mammals captured were wood mouse Apodemus sylvaticus , yellow-necked mouse Apodemus flavicollis , bank vole Clethrionomys glareolus and common shrew Sorex araneus . Small numbers of harvest mice Micromys minutus , field voles Microtus agrestis , pygmy shrews Sorex minutus and water shrews Neomys fodiens were also caught. Wood mouse, the most numerous species, showed a typical pattern of large numbers in autumn and winter, followed by a simultaneous decline over all hedges in early spring. Population changes were less clear in yellow-necked mouse and bank vole but the yellow-necked mouse was more scarce in the second year of study. Common shrews were most numerous in summer and declined rapidly in autumn. Hedgerow coppicing had a marked effect on yellow-necked mouse numbers but not on wood mouse. In an extensive survey of mammal numbers in relation to hedgerow features, ground cover was found to be the single largest factor influencing size of bank vole populations. Hedgerow condition (lack of gaps) was important to yellow-necked mice, which thrived only in well-established hedgerows. Wood mice appeared little influenced by the characteristics of the hedge. Common shrews were more abundant in hedgerows with adjacent permanent water.     

Fluctuations in some small rodent populations in Norway 1971–1979

Small rodent populations were monitored by autumn snap trapping in 22 localities of Norway during the years 1971–979. A total of 105528 trap days yielded 7987 small mammals, out of which the bank vole Clethrionomys glareolus and the short-tailed vole Microtus agrestis made up 52.3 and 29.0%, respectively. Third in abundance was the wood mouse Apodemus sylvaticus .
Both M. agrestis and C. glareolus fluctuated fairly regularly, with general peak years of abundance in 1973 and 1977. Other Microtidae, such as M. oeconomus, C. rutilus and Lemmus lemmus apparently also exhibited cyclic fluctuations. In Arvicola terrestris, Apodemus , and in Sorex shrews, regular fluctuations could not be demonstrated, although the abundance varied considerably.
The body weights of sub-adult C. glareolus cycled in accordance with the fluctuations in abundance; the highest weights being recorded in peak years. In M. agrestis , this correlation was less obvious.     

Borrelia japonica in Nature: Genotypic Identification of Spirochetes Isolated from Japanese Small Mammals

Spirochetes were isolated from earlobe tissues of shrews (Sorex unguiculatus, Sorex caecutiens, and Crocidura dsinezumi), voles (Clethrionomys rufocanus), and mice (Apodemus argenteus and Apodemus speciosus) captured in various localities in Japan. The isolates were identified as Borrelia japonica by rRNA gene restriction fragment length polymorphism analysis. The data suggest that these small mammals are candidates of reservoir hosts for B. japonica.     

The effect of varying calcium intake on calcium metabolism in wild rodent species

Calcium is essential for mammals but distributed heterogeneously in the environment and so the calcium content of the diet of wild small mammals can vary with habitat geology. The effect of varying the calcium intake of two wild rodent species, the granivorous wood mouse Apodemus sylvaticus and the herbivorous bank vole Clethrionomys glareolus , was investigated. Wood mice were similar to laboratory rodents in their calcium metabolism. Net calcium gut absorption efficiency was 11–15% in wood mice fed either high (0˙87%) or low (0˙30%) calcium diet. No more than the equivalent of 6% of the ingested calcium load was excreted in urine but this was sufficient to eliminate the equivalent of all the extra calcium absorbed across the gut when mice were fed the high calcium diet. In contrast, mean net calcium gut absorption efficiency in bank voles was high and increased from 28% to 42% when dietary calcium content was tripled. Urine was important for excreting calcium, the equivalent of up to 23% of intake being eliminated by this route. Despite this, bank voles fed the high calcium diet assimilated three times more calcium than voles fed the low calcium diet; this was in direct proportion to the three-fold difference in dietary calcium concentration. Possible implications for wild rodents in calcium-rich and calcium-poor habitats are discussed.     

Role of small mammals in the persistence of Louping-ill virus: field survey and tick co-feeding studies

Louping-ill (LI) is a tick-borne viral disease of red grouse, Lagopus lagopus scoticus Lath. (Tetraonidae: Galliformes), and sheep, Ovis aries L. (Bovidae: Artiodactyla), that causes economic loss to upland farms and sporting estates. Unvaccinated sheep, grouse and mountain hares, Lepus timidus L. (Leporidae: Lagomorpha), are known to transmit LI virus, whereas red deer, Cenrus elaphus L. (Cervidae: Artiodactyla), and rabbits, Oryctolagus cuniculus L. (Leporidae: Lagomorpha), do not. However, the role of small mammals is unknown. Here, we determine the role of small mammals, in particular field voles, Microtus agrestis L. (Muridae: Rodentia), in the persistence of LI virus on upland farms and sporting estates in Scotland, using field sampling and non-viraemic transmission trials. Small mammals were not abundant on the upland sites studied, few ticks were found per animal and none of the caught animals tested seropositive to LI virus. Laboratory trials provided no evidence that small mammals (field voles, bank voles, Clethrionomys glareolus L. (Muridae: Rodentia), and wood mice, Apodemus sylvaticus L. (Muridae: Rodentia), can transmit LI virus between cofeeding ticks and, in the field, LI virus was prevalent only in areas with known LI virus competent hosts (grouse, mountain hares or unvaccinated sheep) and absent elsewhere. In contrast to the case of tick-borne encephalitis (TBE) virus in Europe, it is concluded that small mammals seem to be relatively unimportant in LI virus persistence.     

The effect of cowpox virus infection on fecundity in bank voles and wood mice.

Although epidemic infectious diseases are a recognized cause of changes in host population dynamics, there is little direct evidence for the effect of endemic infections on populations. Cowpox virus is an orthopoxvirus which is endemic in bank voles (Clethrionomys glareolus), wood mice (Apodemus sylvaticus) and field voles (Microtus agrestis) in Great Britain. It does not cause obvious signs of disease nor does it affect survival, but in this study we demonstrate experimentally that it can reduce the fecundity of bank voles and wood mice by increasing the time to first litter by 20-30 days. The pathogenic mechanisms causing this effect are at present not known, but this finding suggests that natural subclinical infection could have a considerable effect on the dynamics of wild populations.     

Frenkelia parasites in a small mammal community. Dynamics of infection and effect on the host

A community of small mammals, Clethrionomys glareolus, Arvicola terrestris, Microtus arvalis, M. agrestis, M. subterraneus, Apodemus spp. and Sorex spp., was studied as hosts of Frenkelia glareoli and F. microti in Fronche-Comté (France). They were monitored in spring, summer and autumn on an area of about 1,350 ha comprising open field, hedgerow network and forest. Among 1,714 small mammals examined between July 1992 and October 1993, 47% (178/376) of C. glareolus, 9.9% (14/139) of A. terrestris and 1.3% (4/311) of Apodemus spp. were infected by F. glareoli. The prevalence of infection with F. microti was 9.2% (66/716) in M. arvalis and 8.2% (6/73) in M. agrestis. M. subterraneus and Sorex spp. were not infected. The maintenance of each parasite in a rural landscape is assured both by a forest and a grassland host. Multiple logistic regression showed that prevalence was highly age-dependent, with an apparent seasonal pattern. Prevalence varied between 30% in summer and 60% in early spring for F. glareoli in C. glareolus and between 3% in autumn to 30% in early spring for F. microti in M. arvalis. The year, habitat, host sex, relative density had no impact on prevalence. In M. arvalis only, sexually active voles were preferentially uninfected, indicating a possible impact of this parasitism on fertility.     

Dog tick-borne diseases in Sicily

In Sicily many tick borne diseases are endemic, in particular way those that see like main carrier ticks that prefer, for their vital cycle, climatic conditions characterized by high temperatures and a warmth-humid atmosphere. The more important pathologies transmitted by ticks causing diseases in dogs are babesiosis and ehrlichiosis. Borrelia burgdorferi, Anaplasma phagocytophilum, Rickettsia conorii, Coxiella burnetii and tick transmitted encephalitis virus assume particular relevance because they are agents of zoonosis. Our centre, C.R.A.Ba.R.T, have conducted many researches and carried out many tests for diagnostic aim in order to estimate the spread of the main tick borne diseases in Sicilians' dogs. A study lead on 342 dogs has evidenced seroprevalence for Babesia canis, Ehrlichia canis and Rickettsia respective of 5.17%, 21.70% and 53.43%. A study on zoonotic agent seroprevalences in dogs gave the following percentages: C. burnetii 31.50%, R. conorii 73.60% and A. phagocytophilum 32.80%. The data carried out from IZS Sicily diagnostic service on 5,634 tests done in 2004-2005, confirm the experimental results on the presence of B. canis, E. canis, R. conorii, A. phagocytophilum, C. burnetii, Rickettsia spp., Anaplasma spp. and Ehrlichia spp. in all the Sicilian areas.     

The dynamics of murid gammaherpesvirus 4 within wild, sympatric populations of bank voles and wood mice

Murid gammaherpesvirus 4 (MuHV-4) is widely used as a small animal model for understanding gammaherpesvirus infections in man. However, there have been no epidemiological studies of the virus in wild populations of small mammals. As MuHV-4 both infects cells associated with the respiratory and immune systems and attempts to evade immune control via various molecular mechanisms, infection may reduce immunocompetence with potentially serious fitness consequences for individuals. Here we report a longitudinal study of antibody to MuHV-4 in a mixed assemblage of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus) in the UK. The study was conducted between April 2001 and March 2004. Seroprevalence was higher in wood mice than bank voles, supporting earlier work that suggested wood mice were the major host even though the virus was originally isolated from a bank vole. Analyses of both the probability of having antibodies and the probability of initial seroconversion indicated no clear seasonal pattern or relationship with host density. Instead, infection risk was most closely associated with individual characteristics, with heavier males having the highest risk. This may reflect individual variation in susceptibility, potentially related to variability in the ability to mount an effective immune response.     

Transmission dynamics of a zoonotic pathogen within and between wildlife host species

The transmission dynamics of the cowpox virus infection have been quantified in two mixed populations of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus), through analyses of detailed time-series of the numbers of susceptible, infectious and newly infected individuals. The cowpox virus is a zoonosis which circulates in these rodent hosts and has been shown to have an adverse effect on reproductive output. The transmission dynamics within species is best described as frequency dependent rather than density dependent, contrary to the 'mass action' assumption of most previous studies, both theoretical and empirical. Estimation of a transmission coefficient for each species in each population also allows annual and seasonal variations in transmission dynamics to be investigated through an analysis of regression residuals. Transmission between host species is found to be negligible despite their close cohabitation. The consequences of this for the combining ability of hosts as zoonotic reservoirs, and for apparent competition between hosts, are discussed.     

The fruits available as food to small rodents in two woodland ecosystems

The fruit fall from the canopy and the understorey in an oak Quercus petraea (Mattushka) Liebl. wood and in a yew Taxus baccata L. wood at Killarney, Ireland, were measured over a period of approximately 13 months; this included two complete fruit crops in each wood. Fruit represents the great bulk of the food of the small rodents present: wood mice Apodemus sylvaticus (L.) and bank voles Clethrionomys glareolus Schreber. From a knowledge of the particular fruits or their parts eaten, the amounts of available food, in kcal ha^-1 were derived. In each ecosystem the food potentially available to small rodents in one crop was five times that in the other.     

Evidence for different bottom-up mechanisms in wood mouse ( Apodemus sylvaticus ) and bank vole ( Myodes glareolus ) population fluctuations in Southern Norway

Animals that feed on forest tree seeds, such as Apodemus mice, increase in number after a mast year. At high latitudes, there is a similar delayed response by Myodes voles to high seed crops of bilberry (Vaccinium myrtillus), but here the mechanism is hypothesised to be increased forage quality, caused by a trade-off between reproduction and defence in the plants. Both Apodemus mice and Myodes voles eat berries, but only the latter feed on bilberry plants. Hence, only Myodes voles are predicted to respond to bilberry peak years. A second prediction is that the effect should last longer than any possible direct impacts of bilberries, because the plants would not be able to rebuild their defence until the succeeding summer. During a 21-year snap-trapping study of small rodents in Southern Norway, the spring population of bank vole (Myodes glareolus) was positively related to a bilberry seed index of the previous year, indicating increased winter survival, whereas the wood mouse (Apodemus sylvaticus) was not affected. Also the succeeding autumn population index of the bank vole was positively related to the bilberry index of the previous year, even when controlling for spring population levels. The wood mouse population responded to mast years of sessile oak (Quercus petraea), whereas seeds of Norway spruce (Picea abies) seemed to have some impact on both species. It is concluded that these rodents are mainly limited from below, but by different mechanisms for the granivorous and the herbivorous species.     

Testosterone depresses innate and acquired resistance to ticks in natural rodent hosts: a force for aggregated distributions of parasites

The effects of testosterone on acquired resistance to ticks, Ixodes ricinus, in their natural rodent hosts (voles, Clethrionomys glareolus, and wood-mice, Apodemus sylvaticus) were investigated by manipulating testosterone levels and exposing the hosts to repeated tick infestations. Testosterone reduced both innate and acquired resistance to tick feeding. During primary infestations, attachment rates were higher on rodents with high testosterone levels than on oil-implanted controls. Successive infestations on voles were accompanied by a decrease in tick feeding success and survival, but this decrease was significantly greater in ticks fed on control voles than in those fed on voles implanted with testosterone. When reduced feeding success had been induced, either by vaccination with tick salivary gland extract or by 4 successive infestations, implantation with testosterone partially reversed the acquired resistance. These effects of testosterone will generate heterogeneities within the rodent population with respect to tick distribution and microparasite transmission. The lowest innate and acquired resistance to tick feeding occurs in that fraction of the host population, i.e., sexually active males, most actively involved in the transmission of both Babesia microti and Borrelia burgdorferi s.l.     

Serological survey for viral pathogens in Turkish rodents

Wild rodents (n = 330) were trapped around the villages of Altindere and Co?andere (Ma?ka, Trabzon Province), Ayder, Ortan, and Yolkiyi (Camlihem?in, Rize Province), and Bozdag (Odemi?, Izmir Province) in northeastern and western Turkey during April 2004. Samples were tested for arenavirus, hantavirus, and cowpox virus (family Poxviridae, genus Orthopoxvirus, CPXV) antibodies by using immunofluorescence assays (IFAs). Antibodies against arenaviruses were found in eight of 330 (2.4%) rodents. Arenavirus sero-positive animals were found from all study sites. Antibodies to Puumala virus (family Bunyaviridae, genus Hantavirus, PUUV) were detected in four of 65 Microtus voles tested. Of the PUUV-IFA-positive voles, one Microtus guentheri lydius was caught from Izmir, and one Microtus roberti and two Microtus rossiaemeridionalis were captured near Trabzon. All 264 Apodemus spp. mice tested negative for antibodies to Saaremaa virus (family Bunyaviridae, genus Hantavirus, SAAV); the single Dryomys nitedula tested negative for both PUUV and SAAV antibodies. Only one (0.3%) of the rodents, an Apodemus sylvaticus from Trabzon area, tested seropositive to CPXV. This is the first serologic survey for rodent-borne viruses in their natural hosts in Turkey. Although these preliminary results support presence of several virus groups with zoonotic potential, additional studies are needed to identify the specific viruses that are present in these populations.     

Isolation of Emmonsia crescens Emmons et Jellison 1960 from small mammals in Bulgaria

Authors examined a total of 3849 specimens of mammals included in 36 species from different region of Bulgaria. Adiaspiromycosis was detected microscopically in 18 mammals species. Strains of Emmonsia crescens Emmons et Jellison 1960 was isolated from 6 species--Apodemus flavicollis, Apodemus sylvaticus, Clethrionomys glareolus, Microtus arvalis, Musmusculus and Rattus norvegicus.     

Tick-borne rickettsial pathogens in ticks and small mammals in Korea

In order to investigate the prevalence of tick-borne infectious agents among ticks, ticks comprising five species from two genera (Hemaphysalis spp. and Ixodes spp.) were screened using molecular techniques. Ticks (3,135) were collected from small wild-caught mammals or by dragging/flagging in the Republic of Korea (ROK) and were pooled into a total of 1,638 samples (1 to 27 ticks per pool). From the 1,638 tick samples, species-specific fragments of Anaplasma phagocytophilum (1 sample), Anaplasma platys (52 samples), Ehrlichia chaffeensis (29 samples), Ehrlichia ewingii (2 samples), Ehrlichia canis (18 samples), and Rickettsia rickettsii (28 samples) were amplified by PCR assay. Twenty-one pooled and individual tick samples had mixed infections of two (15 samples) or three (6 samples) pathogens. In addition, 424 spleen samples from small captured mammals (389 rodents, 33 insectivores, and 2 weasels) were screened for selected zoonotic pathogens. Species-specific DNA fragments of A. phagocytophilum (110 samples), A. platys (68 samples), E. chaffeensis (8 samples), E. ewingii (26 samples), E. canis (51 samples), and Rickettsia sp. (22 samples) were amplified by PCR assay. One hundred thirty small mammals had single infections, while 4, 14, and 21 striped field mice (Apodemus agrarius) had mixed infections of four, three, and two pathogens, respectively. Phylogenetic analysis based on nucleotide sequence comparison also revealed that Korean strains of E. chaffeensis clustered closely with those from China and the United States, while the Rickettsia (rOmpA) sequences clustered within a clade together with a Chinese strain. These results suggest that these agents should be considered in differential diagnosis while examining cases of acute febrile illnesses in humans as well as animals in the ROK.     

NMR spectroscopy based metabonomic studies on the comparative biochemistry of the kidney and urine of the bank vole (Clethrionomys glareolus), wood mouse (Apodemus sylvaticus), white toothed shrew (Crocidura suaveolens) and the laboratory rat

The metabolic profiles of three wild mammals that vary in their trophic strategies, the herbivorous bank vole (Clethrionomys glareolus), the granivorous wood mouse (Apodemus sylvaticus), and the insectivorous white-toothed shrew (Crocidura suaveolens), were compared with that of a widely used strain of laboratory rat (Sprague Dawley). In conjunction with NMR spectroscopic investigations into the urine and blood plasma composition for these mammals, high resolution magic angle spinning (HRMAS) 1H-nuclear magnetic resonance (NMR) spectroscopy was applied to investigate the composition of intact kidney samples. Adaptation to natural diet affects both renal metabolism and urinary profiles, and while these techniques have been used to study the metabolism of the laboratory rat little is known about wild small mammals. The species were readily separated by their urinary profiles using either crude metabolite ratios or statistical pattern recognition. Bank vole urine contained higher concentrations of aromatic amino acids compared with the other small mammals, while the laboratory rats produced relatively more hippurate. HRMAS 1H-NMR demonstrated striking differences in both lipid concentration and composition between the wild mammals and Sprague Dawley rats. Bank voles contained high concentrations of the aromatic amino acids phenylalanine, tyrosine and tryptophan in all tissue and biofluids studied. This study demonstrates the analytical power of combined NMR techniques for the study of inter-species metabolism and further demonstrates that metabolic data acquired on laboratory animals cannot be extended to wild species.     

The trophic impact of small mammals in successional grasslands

The habitat use and diets of small mammals inhabiting grassland plots of different successional ages were investigated by live-trapping and faecal analysis over a period of 16 months. The contribution of the major plant life forms and the structural profile of the vegetation of each plot and the availability of insect prey were assessed. The dominant species of small mammal found on each plot were Sorex araneus, S. minutus, Apodemus sylvaticus and Microtus agrestis . Small mammals were most commonly found in the late and mid-successional stages, reflecting the habitat structure and food availability. A wide range of insects and other invertebrates were eaten by all four species and insects formed 50–62% of the animal prey taken. The incidence of certain prey in the diets differed between plots. The daily consumption rate of invertebrates by shrews and mice was estimated at some 6800 prey per ha. The greatest predatory impact came from shews but A. sylvaticus showed increased consumption of invertebrates in spring. The combined predatory impact of the grassland small mammal community on insect populations alone was estimated to average 0.01% per day and is predicted to be greatest in the mid-successional stages.     

Observations of fleas of small mammals at the Gran Paradiso National Park (Italian Occidental Alps)]

The Siphonaptera of small mammals (nearly 200 rodents, insectivora and mustelids) of the Parco Nazionale del Gran Paradiso (Western Italian Alps) have been collected and studied during the years 1973-75. All the animals have been captured at altitudes ranging from 1570 to 2400 m during different seasons. Twelve genera and sixteen species have been identified, namely: Chaetopsylla (C.) homoea homoea from Mustela erminea; Hystrichopsylla (H.) talpae talpae from Clethrionomys glareolus; Rhadinopsylla (A.) integella integella from Clethrionomys glareolus and Microtus nivalis; Ctenophtalmus (C.) agyrtes verbanus from Pitymys multiplex (collected by Beaucournu); Ctenophthalmus (C.) solutus solutus from Apodemus flavicollis and Apodemus sylvaticus; Ctenophthalmus (Medioctenophthalmus) nivalis nivalis from Clethrionomys glareolus, Microtus nivalis and Pitymys multiplex; Doratopsylla dasycnema cuspis from Sorex araneus and Clethrionomys glareolus; Palaeopsylla soricis rosickyi from Sorex araneus; Leptopsylla segnis from Apodemus sylvaticus and Mus musculus; Peromyscopsylla bidentata bidentata from Clethrionomys glareolus and Microtus nivalis; peromyscopsylla fallax from clethrionomgs glareous; Amphipsylla sibirica ssp. from clethrionomys glareolus and microtus nivalis; Malaraeus (Amalaraeus), penicilliger kratachvili from Clethrionomys glareolus, Microtus nivalis and Mustela erminea; Myoxopsylla laverani from Eliomys quercinus; Callopsylla saxatilis from Apodemus flavicollis, Microtus nivalis and Mustela erminea. Species of fleas not yet described in Italy are: Chaetopsylla (C.) homoea homoea; Rhadinopsylla (Actenophthalmus) mesa; Ctenophthalmus (Medioctemophthalmus) nivalis nivalis; Callopsylla saxatilis. The genus Callopsylla is identified for the first time in Italy. New identification of hosts for the species of fleas already described in Italy are: for Rhadinopsylla (Actenophthalmus) integella integella: Clethrionomys glareolus; for Ctenophthalmus (C.) solutus solutus: Apodemus flavicollis and Apodemus sylvaticus. All the 15 male specimens of M. laverani from E. quercinus captured in the Parco Nazionale del Gran Paradiso have characters more similar to M. l. traubi than to M. l. laverani: only one long and a much shorter spine in the superior half of the movable process, a distinct tooth in the anterior margin of the movable half of the movable process, a distinct tooth in the anterior margin of the movable process, crochets of phallosome shorter and more gradually tapered, apex of fixed process very acuminated. To the contrary the shape of the movable process is similar to that of M. l. laverani. A point of particular interest is to be found also in 2 specimens of Amphypsilla of the sibirica group, respectively collected from Mustela erminea and Microtus nivalis. They have a very atypical distribution of the spine in an abnormally shaped movable process: the reasons of the abnormality are due to castration, probably of parasitic origin (absence of phallosome, tendons, etc.).