Experimental Toxoplasma gondii infection in striped skunk (Mephitis mephitis)

Twenty-three striped skunks (Mephitis mephitis) without demonstrable antibodies in 1:25 serum dilution in the modified agglutination test (MAT) were fed sporulated Toxoplasma gondii oocysts (9 skunks) or tissue cysts (10 skunks), and 4 skunks (controls) were not fed T. gondii. Skunks were bled before feeding T. gondii, 10 and 23- 25 days postinoculation (PI). All 9 seronegative skunks fed oocysts died of acute toxoplasmosis between 7 and 19 days PI; T. gondii tachyzoites were found in histological sections of many tissues. One of the 10 skunks fed tissue cysts and 1 of the 4 controls also died of acute toxoplasmosis days 19 and 20 PI; these animals probably became infected by ingestion of unexcysted oocysts passed in feces of skunks fed oocysts that were housed in the same room that skunks fed tissue cysts were housed. The remaining 9 skunks fed tissue cysts and the 3 controls developed only a mild illness and were killed in good health on days 23-25 PI. Antibodies to T. gondii were not found in 1:25 serum dilution of any of the 19 of 23 skunks that were alive on day 10 PI; 12 of 13 skunks had antibodies (MAT 1:80 or higher) on the day they were killed. Antibodies were not found in 1 skunk. Results indicate that skunks can develop IgG antibodies to T. gondii within 3 wk PI, and primary toxoplasmosis can be fatal in skunks.     

Ineffectiveness and comparative pathogenicity of attenuated rabies virus vaccines for the striped skunk (Mephitis mephitis)

Three attenuated rabies virus vaccines (SAD-B19, ERA/BHK-21, AZA 2) were compared for efficacy and safety in the striped skunk (Mephitis mephitis) by the oral and intranasal routes. The SAD-B19 and ERA/BHK-21 vaccines were given orally; all three vaccines were given intranasally. Oral administration of SAD-B19 and ERA/BHK-21 vaccines induced neither seroconversion nor significant protection against rabies challenge. One skunk which consumed a SAD-B19 vaccine-laden bait succumbed to vaccine-induced rabies. Intranasal instillation of the three vaccines resulted in the deaths of two of six (AZA 2), three of six (ERA/BHK-21) and six of six (SAD-B19) skunks.     

Rabies challenge of captive striped skunks (Mephitis mephitis) following oral administration of a live vaccinia-vectored rabies vaccine

Twenty-four adult striped skunks (Mephitis mephitis) were administered the raccoon product formulation of Rabies Vaccine, Live Vaccinia-Vectored (Raboral V-RG, Merial Limited, Athens, Georgia, USA), either by oral instillation or in vaccine-filled coated sachets either as single or multiple doses. A control group remained unvaccinated. Twenty-three of the skunks were challenged 116 days postvaccination with rabies virus (skunk isolate). Six of six naive skunks succumbed to challenge. Four of six skunks that received the vaccine by oral instillation survived challenge. The skunks that did not survive failed to seroconvert following vaccination. None of the skunks that accepted multiple doses of the vaccine offered in coated sachets survived challenge, nor were rabies virus-neutralizing antibodies (VNAs) detected in the sera. Likewise, none of the five skunks ingesting a single sachet developed VNA against rabies. However, in this group one skunk did survive rabies challenge. This preliminary study showed that the vaccinia-vectored oral rabies vaccine Raboral V-RG, as formulated for use in raccoons, is capable of protecting a percentage of skunks against rabies. However, although the fishmeal-coated sachets were readily consumed, subsequent challenge of these animals revealed poor vaccine delivery efficiency.     

The striped skunk (Mephitis mephitis) is an intermediate host for Sarcocystis neurona

Striped skunks, initially negative for antibodies to Sarcocystis neurona, formed sarcocysts in skeletal muscles after inoculation with S. neurona sporocysts collected from a naturally infected Virginia opossum (Didelphis virginiana). Skunks developed antibodies to S. neurona by immunoblot and muscles containing sarcocysts were fed to laboratory-reared opossums which then shed sporulated Sarcocystis sporocysts in their faeces. Mean dimensions for sporocysts were 11.0 x 7.5 microm and each contained four sporozoites and a residuum. Sarcocysts from skunks and sporocysts from opossums fed infected skunk muscle were identified as S. neurona using PCR and DNA sequence analysis. A 2-month-old, S. neurona-naive pony foal was orally inoculated with 5 x 10(5) sporocysts. Commercial immunoblot for antibodies to S. neurona performed using CSF collected from the inoculated pony was low positive at 4 weeks p.i., positive at 6 weeks p.i., and strong positive at 8 weeks p.i. Gamma-interferon gene knockout mice inoculated with skunk/opossum derived sporocysts developed serum antibodies to S. neurona and clinical neurologic disease. Merozoites of S. neurona present in the lung, cerebrum, and cerebellum of mice were detected by immunohistochemistry using polyclonal antibodies to S. neurona. Based on the results of this study, the striped skunk is an intermediate host of S. neurona.     

Polymorphic microsatellite markers for the striped skunk, Mephitis mephitis, and other mephitids

We report 10 polymorphic microsatellite loci primers developed for striped skunks (Mephitis mephitis), a widespread mesocarnivore in North America. Numbers of alleles in these loci ranged from seven to 14 and the observed heterozygosity ranged from 0.76 to 1.0. These primers will be useful for studying population dynamics of skunks where rabies is endemic and will be useful to estimate genetic relatedness among females sharing winter dens. Most of these primers amplify across species within the Mephitidae.     

Genetic stability (in vivo) of the attenuated oral rabies virus vaccine SAD B19

The distribution of oral rabies vaccine baits containing replication-competent live viruses poses certain environmental safety risks; among others, the possibility of reversion to or an increase in virulence. Hence, the genetic stability of the complete genome of the most widely used oral rabies vaccine virus, SAD B19, was examined after four and 10 serial i.c. passages in foxes and mice, respectively. It was shown that the consensus strain of SAD B19 was extremely stable in vivo . After 10 consecutive passages in mice not a single mutation was observed. In foxes, seven single nucleotide exchanges were found between the first and fourth passage, of which only one resulted in an amino acid exchange at position 9240 of the L-gene. This mutation was not observed during the first three passages and, furthermore, it was shown that this mutation was not linked to enhanced virulence.     

Rabies and rabies control in striped skunks (Mephitis mephitis) in three prairie regions of western North America

The number and geographic distribution of rabies cases in striped skunks (Mephitis mephitis) from Saskatchewan (n = 2,506 cases), Montana (n = 1,142), and Alberta (n = 199) since 1963 were reviewed. In Saskatchewan the number of cases increased steadily for 5 yr and then fluctuated consistently in a 4 yr cyclic pattern. Similarly an initial sweep across the province was followed by a cyclic pattern of geographic expansion (3 to 4 yr) and reduction (1 to 2 yr). No organized control efforts were conducted in Saskatchewan. Similar cyclic pattern were not seen in data from Montana or Alberta. In the latter areas, the number and distribution of rabies cases in skunks appeared to reflect efforts to reduce the population of skunks. An integrated program of skunk removal using poison and live-traps in association with research and public education successfully contributed to limiting the spread and establishment of rabies in striped skunks within prairie habitats. Rabies did not persist in skunks in other habitats.     

Hypothalamic neurosecretory activity in relation to the reproductive cycle in the common striped skunk (Mephitis mephitis nigra; order carnivora)

Summary The histological appearance of certain cell groups in the anterior hypothalamus was studied during various phases of the reproductive cycle of the common striped skunk (Mephitis mephitis nigra), a carnivore having a very restricted period of sexual activity. Pronounced changes occur in the amount of stainable neurosecretory material in cells of the supraoptic, paraventricular and anterior hypothalamic nuclei. Material staining with aldehyde fuchsin is stored (or inhibited from being released) in these cells during the sexually quiescent period in both the female and male skunk. The time of approaching sexual activity is characterized by the first signs of release of neurosecretory material from these hypothalamic cells and the peak of estrus and rut coincides with a minimal content of the material.Dedicated to Professor Berta V. Scharrer in honor of her 60th birthday.This study was supported by U.S.P.H.S. Training Grant 5 T 1-GM 102 and Research Grant BN-00840, from the National Institutes of Health. This represents a portion of a dissertation, written under the guidance of the late Professor Ernst Scharrer, and submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Yeshiva University, June, 1965. Preliminary reports of this work were presented at the 78th annual session of the American Association of Anatomists, Miami, Florida, and at the VIIIth International Congress of Anatomists, Wiesbaden, Germany, (Hagedoorn, 1965a, b). I thank Dr. H. W. Deane and Dr. J. Osinchak for their critical reading of this manuscipt.     

Streptococcus equisimilis infection in striped skunks (Mephitis mephitis) in Saskatchewan

Three radio-collared striped skunks (Mephitis mephitis) found dead during a field study of winter ecology of striped skunks near Willowbrook, Saskatchewan, Canada were examined. Streptococcus equisimilis was identified as the primary agent causing necrotizing purulent pneumonia in one skunk and suppurative meningoencephalitis in another. Both Streptococcus equisimilis and Streptococcus canis were isolated from lesions of purulent myocarditis and pyothorax in the third skunk. These are apparently the first reported cases of S. equisimilis infection in striped skunks and suggest that this opportunistic pathogen may be a significant cause of mortality under some conditions.     

Seasonal and daily activity patterns of striped skunks (Mephitis mephitis) in the Canadian prairies

We investigated the hypothesis that the daily and seasonal activity patterns of female and male striped skunks ( Mephitis mephitis ) vary with reproductive constraints. Four biological periods were identified: pre-parturition (1 April–14 May), parturition and rearing (15 May–30 June), pre-dispersal (1–31 July), and dispersal (1–31 August). Tracking data (1873h) indicated that activity (percentage time active) of female skunks varied among seasons, being lowest during the pre-parturition period (34 ± 10%), and highest during the pre-dispersal period (66 ± 4%). Male activity did not vary among seasons (55 ± 3%). Animals of both sexes were mostly nocturnal, and had similar patterns of daily activity. Onset and cessation of activity were highly variable, but were not affected by season or sex. Daily activity typically started 13 ± 10 min before sunset, and was terminated 35 ± 8min before sunrise. Night-time activity periods of both sexes were often (57%, n = 108) interrupted by at least one resting period (median = 1, range = 0–4). However, females rarely (5%, n = 89) returned to the maternal den to rest. We hypothesize that the nocturnal activity of adults is linked to prey activity and reduced predation risk, whereas apparent diurnal activity of juveniles represents an adaptation to daily fasting periods caused by the nocturnal foraging trips of females.     

Toxoplasmosis, distemper, and herpesvirus infection in a skunk (Mephitis mephitis).

A striped skunk (Mephitis mephitis) showing abnormal behavior had histopathologic lesions of toxoplasmosis and canine distemper in addition to intranuclear, eosinophilic inclusions in the reticuloendothelial cells of the spleen, liver and lung. The inclusions, on electron microscopic examination, were compatible with herpesvirus infection.     

Energetic consequences and ecological significance of heterothermy and social thermoregulation in striped skunks (Mephitis mephitis)

We assessed patterns and energetic consequences of different overwintering strategies, torpor, and social thermoregulation in the striped skunk (Mephitis mephitis) under natural ambient temperature and photoperiod. Striped skunks entered spontaneous daily torpor, with the lowest torpid body temperature (T(b)) reaching 26.0 degrees C, the lowest recorded T(b) for a carnivore. Patterns of daily torpor differed between solitary and grouped skunks: all solitary skunks regularly entered daily torpor, but only some individuals in communal dens employed torpor. When they did, it was shallow and infrequent. Solitary skunks entered torpor on average 50 times (in 120 d) compared with 6 times for grouped skunks. During torpor, solitary skunks had average minimum T(b) of 26.8 degrees C and bout duration of 7.8 h, whereas grouped skunks had average minimum T(b) of 30.9 degrees C and bout duration of 5.4 h. Torpor by solitary skunks occurred during their activity phase, but grouped skunks' shallow torpor bouts were restricted to their diurnal resting phase. On average, grouped skunks experienced lower percent daily fat loss, and they emerged in spring with higher percent body fat of 25.5%. In contrast, solitary skunks emerged in spring with only 9.3% body fat. In conclusion, the use of daily torpor and social thermoregulation in northern populations of striped skunks represent two strikingly different mechanisms to minimize energetic costs and increase individual fitness in response to unfavorable environmental conditions.     

Care, management, and biology of captive striped skunks (Mephitis mephitis).

The striped skunk has a number of characteristics that make it one of the most desirable wild carnivores for scientific study. This paper described in detail the care and management of this species in captivity. Reproduction and factors which may affect productivity were discussed, including: duration of mating period, experience, and age of the female. Two optimal mating periods resulted in the greatest productivity and survival of young: (1) 24 hours and (2) 24 hours followed by another mating of equal duration 2 or 3 da later. Experienced females required fewer matings, conceived earlier, and had larger litters than their inexperienced counterparts. Captive skunks conceived as early as mid-February; births occurred in May or June with litters averaging 4.17 pups per litter. Females produced their maximum number of young at age 2 and had a progressive decline in mean litter size after this age. Measurements of growth and development of the young up to 32 da were included. A descenting method used in descenting nearly 300 pups was described. Mortality was high during the first 2 mo of life, with only 59.81% (192/321) of the pups surviving until weaning. Sixteen different pathologic conditions confirmed by necropsy were listed. The signs of canine distemper in the striped skunk were described.     

Rabies detection in road-killed skunks (Mephitis mephitis)

Three diagnostic techniques (1) microscopic examination for Negri bodies, (2) mouse inoculation and (3) fluorescent antibody tagging were compared as to their ability to detect rabies virus in 14 experimentally infected striped skunks (Mephitis mephitis) exposed to normal summer weather conditions after death. The fluorescent antibody technique correctly identified rabies virus longer than either of the other methods. Rabies incidence in 61 road-killed skunks collected on the day following death in southeastern North Dakota was 26 per cent.