Transmission studies with the contagious equine metritis bacterium in albino Swiss mice

Aspects of experimental transmission of the causal bacterium of contagious equine metritis (CEM) to albino Swiss mice were investigated. Whereas infection was established in the majority of female mice, the organism was recovered from only a limited number of male mice after challenge. No clinical evidence of infection was observed in the experimental mice. There was only one instance of presumptive venereal transmission of the CEM bacterium. One third of infected females conceived and had normal litters.     

Tumor necrosis factor alpha levels in cats experimentally infected with feline immunodeficiency virus: effects of immunization and feline leukemia virus infection.

Tumor necrosis factor alpha (TNF alpha) levels were determined by enzyme-linked immunosorbent assay (ELISA) and by cell culture bioassay in supernatants of lipopolysaccharide-stimulated feline monocyte cultures and in cat serum samples. There was a good correlation between the results obtained by the two methods. From the fact that TNF alpha was neutralized quantitatively by antibodies to human TNF alpha in feline monocyte supernatants and in feline sera, it was concluded that feline TNF alpha immunologically cross-reacts with human TNF alpha and that the human TNF alpha ELISA can be used to quantitate feline TNF alpha. During the first 6 months after experimental feline immunodeficiency virus (FIV) infection no differences in serum TNF alpha values were observed between infected and non-infected cats. TNF alpha levels increased significantly after primary vaccination with a feline leukemia virus (FeLV) vaccine in FIV infected cats over those in the non-infected controls. During secondary immune response TNF alpha levels rose transiently for a period of a few days in both the FIV positive and the FIV negative cats. After FeLV challenge, TNF alpha levels increased in all animals challenged with virulent FeLV for a period of 3 weeks. This period corresponded to the time necessary to develop persistent FeLV viremia in the control cats. It was concluded from these experiments that in the asymptomatic phase of FIV infection no increased levels of TNF alpha are present, similar to the situation in asymptomatic HIV infected humans. Activation of monocytes/macrophages in FIV infected cats by stimuli such as vaccination or FeLV challenge readily leads to increased levels of TNF alpha.     

Feline giardiasis: observations on natural and induced infections

The excretion of Giardia sp cysts in the feces of naturally and artificially infected cats fluctuated sporadically, and cysts were undetectable several times during 7 weeks of observation. The mean prepatent period for Giardia infection in 7 cats was 9.6 days (range, 5 to 16 days). The amount of the cyst inoculum did not appear to affect the length of the prepatent period. Six of 11 cats had clinical signs consistent with those of giardiasis. Clinical signs and cyst excretion were eliminated after treatment with metronidazole or furazolidone. Moderate oral or parenteral doses of corticosteroids produced little, if any, alteration in the infection. Postmortem examination of 1 inoculated cat revealed Giardia trophozoites in the jejunum and upper portion of the ileum but not in the duodenum, lower portion of the ileum, cecum, or colon. Giardia cysts isolated from cat feces produced infection in Mongolian gerbils but not in C57BL/6J mice.     

Prevalence of Chlamydia psittaci in different cat populations in Britain

The prevalence of Chlamydia psittaci infection in household, feral and farm cats in Britain was investigated. Chlamydia were isolated from 30 per cent of conjunctival swabs collected from 753 household cats with conjunctivitis. The prevalence of active chlamydial infection was highest in cats in the age group five weeks to nine months. Males were more frequently infected than females. Cats with chlamydial conjunctivitis usually had antibody titres greater than 1024 as assessed by indirect immunofluorescence. Chlamydia appeared to be endemic in two out of three feral cat colonies on the basis of serological evidence and occasional isolations. Cats on 10 of 22 sheep farms (45 per cent) had serological evidence of chlamydial infection, and this was confirmed on two farms by isolation of the organism from conjunctival and, or, rectal swabs. This is the first survey of infection with Chlamydia psittaci in cat populations in Britain.     

Efficacy and safety field trials of a recombinant DNA vaccine against feline leukemia virus infection.

A new recombinant gp70 vaccine was found to be safe and effective for prevention of infection by FeLV. The vaccine incorporates a unique purified saponin adjuvant with the recombinant antigen. Serious systemic reactions were not observed during the efficacy trial. Local reactions were transient and mild. More than 2,000 doses were administered to a cross section of household cats in a field safety trial. Only 1 cat had hypersensitivity reaction, which resolved. Among veterinarians who used the vaccine and the cat owners, the vaccine was judged satisfactory and safe. After rigorous intraperitoneal challenge exposure without use of immunosuppressants, 100% of the controls in the efficacy trial became infected, 70% of which remained persistently infected with FeLV. Among vaccinates, 45% were never viremic and 40% cleared transient infection within 12 weeks after challenge exposure. Of the 20 vaccinated cats, 3 were persistently infected. Overall, 85% of cats vaccinated with this recombinant DNA FeLV vaccine resisted persistent FeLV infection after stringent challenge exposure, which translates to preventable fraction of 78.6%.     

Diagnosis of Aelurostrongylus abstrusus and Dirofilaria immitis infections in cats from a human shelter

During a 6-month period, 108 sexually mature stray cats were euthanatized at a humane shelter in Alabama. Aelurostrongylus abstrusus was identified in 20 of the cats (18.5%) by Baermann fecal examination, necropsy, or histologic examination. The Baermann fecal examination was a more sensitive test for aelurostrongylosis than was necropsy or histologic examination. Thoracic radiography was useful in identifying infected cats, but was a less sensitive and more nonspecific method of detection than was the fecal examination. Changes in CBC and serum protein concentrations were not helpful identifying cats with aelurostrongylosis. Six of 17 (35%) heartworm-free, lungworm-infected cats had antibodies to Dirofilaria immitis, as determined by an ELISA method, but none had circulating D immitis antigen, as determined by an ELISA method. Three (2.8%) cats had D immitis. Two of the heartworm-infected cats had no detectable antemortem radiographic or clinicopathologic evidence of the infection. Results of ELISA were positive for antibodies to adult heartworms in 2 cats and for circulating heartworm antigen in 2 cats. One cat that had only one heartworm had no detectable circulating heartworm antigen.     

Experimentally induced infection of cats with Borrelia burgdorferi.

To determine whether cats could be infected experimentally with Borrelia burgdorferi, 15 cats were inoculated with approximately 1,000 B burgdorferi. Seven cats were inoculated by the IV route, 2 by the oral route, 2 by the ocular route, and 4 by the oral-ocular route. Six control cats were inoculated with phosphate-buffered saline solution by the IV, oral, and ocular routes. Prior to the start of the study, all 21 cats were seronegative for B burgdorferi on the basis of results of the indirect fluorescent antibody (IFA) test, and their blood was B burgdorferi culture negative. All of the IV, orally, and ocularly inoculated cats developed IgG antibodies to B burgdorferi as detected by IFA testing. Of 4 oral-ocularly inoculated cats, 2 developed IFA-detectable antibodies and the remaining 2 cats developed low-titer response (1:128) on postinoculation (PI) day 10 only. All control cats remained seronegative. The organism was detected in blood smears from 2 of the IV inoculated cats on PI days 10 and 24 and from 2 oral-ocularly infected cats, 1 on PI days 17 and 24 and 1 on PI day 10. Spirochetes were not detected in the blood after PI day 24. The organism was isolated from tissues of only 1 cat (the lung of an ocularly inoculated cat necropsied at 7 months after inoculation). Spirochetes were not isolated from control cats. Neither clinical signs of infection nor gross or histologic abnormalities were found in any of the inoculated or control cats. Results indicate that cats are susceptible to infection with B burgdorferi, but clinically apparent disease may not be common.     

Experimental transmission of Cytauxzoon felis from bobcats (Lynx rufus) to domestic cats (Felis domesticus)

Freshly collected blood and/or spleen homogenate from an experimentally infected Florida bobcat (Lynx rufus floridanus), which had died of feline cytauxzoonosis, was inoculated into domestic cats. All inoculated cats had clinical signs of feline cytauxzoonosis and died within 2 weeks after they were inoculated. Similar material collected from an eastern bobcat (Lynx rufus rufus) carrying an experimentally infected Cytauxzoon felis parasitemia was inoculated into domestic cats. All inoculated cats developed a parasitemia, but none developed clinical signs of disease and none died of the disease. Cats subinoculated with parasitemic cat blood also developed parasitemias and they too did not develop clinical signs of infection nor died. After carrying the blood phase of Cytauxzoon felis for various periods, the domestic cats were then challenge exposed with proven lethal Cytauxzoon inoculum of domestic cat origin. All cats died of cytauxzoonosis.     

Evaluation of praziquantel for treatment of experimentally induced paragonimiasis in dogs and cats

Praziquantel was used successfully for treatment of a small number of dogs and 1 cat infected with Paragonimus kellicotti. To further evaluate the usefulness of this drug in treating such infections, 7 cats and 7 dogs were inoculated orally with metacercariae (12 and 20 to 22, respectively) obtained from crayfish, then were treated after the infections became patent; 2 cats and 2 dogs served as noninfected controls. Beginning 1 week before infection, and continuing weekly thereafter, physical, hematologic, and fecal examinations were performed on each animal; thoracic radiography was performed every other week. By postinoculation week 6, all dogs given metacercariae had patent infection diagnosed on the basis of positive results of fecal examination. By postinoculation week 7, 5 cats had confirmed patent infection, but 2 cats given metacercariae never had patent infection or had signs of infection. Clinical signs of infection were minor and included increased respiratory tract noise, slight inducible cough, or mild dyspnea. Transient eosinophilia was detected in dogs around postinoculation week 3. Pretreatment radiography revealed cavitated lesions in cats only; pleural lines and patchy infiltrates in cats and dogs; or pneumothorax in dogs only. The treatment regimen consisted of 23 mg of praziquantel/kg of body weight given every 8 hours for 3 days; 1 infected cat and dog were not treated. By 11 days after treatment, eggs had disappeared from the feces of infected animals, and marked resolution of lung lesions was evident radiographically.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pathogenesis of feline enteric coronavirus infection

Fifty-one specific pathogen-free (SPF) cats 10 weeks to 13 years of age were infected with a cat-to-cat fecal-oral passed strain of feline enteric coronavirus (FECV). Clinical signs ranged from unapparent to a mild and self-limiting diarrhea. Twenty-nine of these cats were FECV na?ve before infection and followed sequentially for fecal virus shedding and antibody responses over a period of 8-48 months. Fecal shedding, as determined by real-time polymerase chain reaction (RT-PCR) from rectal swabs, appeared within a week and was significantly higher in kittens than older cats. FECV shedding remained at high levels for 2-10 months before eventually evolving into one of three excretion patterns. Eleven cats shed the virus persistently at varying levels over an observation period of 9-24 months. Eleven cats appeared to have periods of virus shedding interlaced with periods of non-shedding (intermittent or recurrent shedders), and seven cats ceased shedding after 5-19 months (average 12 months). There was no change in the patterns of virus shedding among cats that were excreting FECV at the time of a secondary challenge exposure. Four cats, which had ceased shedding, re-manifested a primary type infection when secondarily infected. Cats with higher feline coronavirus (FCoV) antibody titers were significantly more likely to shed virus, while cats with lower titers were significantly less likely to be shedding. Twenty-two kittens born to experimentally infected project queens began shedding virus spontaneously, but never before 9-10 weeks of age. Natural kittenhood infections appeared to be low grade and abortive. However, a characteristic primary type infection occurred following experimental infection with FECV at 12-15 weeks of age. Pregnancy, parturition and lactation had no influence on fecal shedding by queens. Methylprednisolone acetate treatment did not induce non-shedders to shed and shedders to increase shedding.     

Infection patterns in pony mares challenged with the agent of contagious equine metritis 1977

Contagious equine metritis 1977 was reproduced in pony mares using cultures of the Gram-negative coccobacillus aetiologically associated with the disease. Variability in clinical response was observed in the first of 2 experiments, with the presence of semen, either alone or in an extender, appearing to potentiate the pathogenicity of the challenge strain of the organism. The experimental disease was characterised by a variable degree of vaginal discharge and concomitant inflammatory changes involving the vervix and vagina. Although all of the affected mares recovered spontaneously, a high percentage continued to harbour the Gram-negative coccobacillus in their genital tracts for variable periods after challenge. Shedding of the organism was either relatively constant or intermittent and was not solely related to the oestrous period. Cytological examination of smears of cervical and urethral swabs was of diagnostic value only during the clinical phase of the infection. There was evidence that reinfection of mares could occur after an interval of 2 weeks.     

Efficacy of Giardia vaccination in the treatment of giardiasis in cats

OBJECTIVE: To assess efficacy of Giardia vaccination as a treatment for giardiasis in experimentally infected cats. DESIGN: Original study. ANIMALS: 16 young-adult cats. PROCEDURE: Cats were experimentally infected by orogastric administration of Giardia cysts. On weeks 4, 6, and 10, cats in the treatment group (n = 8) were given Giardia vaccine SC. For the first 28 weeks after infection, 3 fecal samples from each cat were examined weekly for Giardia cysts, and cyst numbers were counted. Fecal consistency was scored daily for the duration of the study. Results from vaccinated and unvaccinated cats were compared by logistic regression. RESULTS: All cats became infected and were shedding Giardia cysts by the end of week 2. Throughout the study, diarrhea was rare and was mild and transient when it did occur. By week 28, 5 of 8 vaccinated cats and 7 of 8 control cats had patent Giardia infections. Magnitude of infection, based on number of fecal samples with cysts and number of cysts per sample, decreased progressively in both groups over time. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of 3 doses of a Giardia vaccine did not completely eliminate the organism from experimentally infected cats in the study period. Since clinical signs were minimal in both groups of cats, it could not be determined whether vaccination lessened severity of clinical disease. Results may have been negatively influenced by the large inoculation dose. Whether Giardia vaccination is an effective treatment for giardiasis in naturally infected cats remains to be determined.     

Identification of Pentatrichomonas hominis in feline fecal samples by polymerase chain reaction assay

Pentatrichomonas hominis is considered to be a commensal protozoan of the vertebrate digestive tract. On the basis of light microscopic examination of feces, some investigators presumptively identified P. hominis as a causative agent of feline diarrhea. However, molecular identification of P. hominis infection in the cat has not been reported. Another trichomonad, Tritrichomonas foetus, is recognized as an intestinal pathogen in cats and often presumptively diagnosed on the basis of the presence of trichomonads in diarrheic feces. It is of importance to determine if cats are natural hosts for P. hominis, as the presence of this organism could result in inaccurate assumption of T. foetus infection. In this study, we used a species-specific PCR assay to identify P. hominis 18S rRNA genes in fecal samples collected from a convenience population of cats in which a high prevalence of T. foetus infection had been previously identified (cat show) or suspected (submitted for T. foetus diagnostic testing). The prevalence of T. foetus infection in these samples was 31% and 28.6%, respectively. P. hominis infection was identified by PCR of DNA extracted from feces of five cats (1.9% and 2.1% of fecal samples, respectively). All cats in which P. hominis was identified were also infected with T. foetus. PCR identification of P. hominis infection in the cat should facilitate future studies to determine the pathogenicity of this species and enable differentiation of P. hominis from other known or as-yet unidentified species of trichomonads that may infect cats.     

Comparison of the Polymerase Chain Reaction and Culture for the Detection of Feline Chlamydia psittaci in Untreated and Doxycycline-Treated Experimentally Infected Cats

The diagnostic sensitivity of the polymerase chain reaction (PCR) was compared with that of culture on conjunctival swabs over the course of infection in 4 doxycycline-treated and 4 untreated cats that were experimentally infected with feline Chlamydia psittaci. Treated cats were given 25 mg (5 mg/kg) of doxycycline orally twice daily for 3 weeks from day 6 after challenge. Clinical signs improved within 3 days of institution of treatment. Culture remained positive for 1 day and PCR remained positive for up to 5 days after treatment was commenced. No recurrence of clinical signs occurred and the organism could not be detected by either PCR or culture for 2 weeks after cessation of therapy. In the 4 untreated cats, conjunctival swabs were taken daily to day 14 and every 2nd weekday to day 64 after challenge. PCR was significantly more sensitive than culture in untreated cats overall (PCR 85.7%, culture 72.9%, P approximately 0) and for cats with clinical signs (PCR 89.2%, culture 79.2%, P = .008). PCR and culture had equivalent sensitivity (100%) for cats showing clinical signs in the 1st month of infection, whereas PCR was considerably more sensitive than culture for cats showing clinical signs in the 2nd month (PCR 72.9%, culture 47.9%, P = .028). Organisms were not detected by PCR in blood or any tissue collected from treated or untreated cats at postmortem. Thus, effective treatment of chlamydiosis in cats is possible with much shorter treatment regimens than currently recommended, and PCR is the more sensitive diagnostic method in chronically infected cats.     

In vivo transmission studies of ��Candidatus Mycoplasma turicensis�� in the domestic cat

The natural transmission routes of the three feline haemotropic mycoplasmas – Mycoplasma haemofelis, ‘Candidatus Mycoplasma haemominutum’, and ‘Candidatus Mycoplasma turicensis’ (CMt) – are largely unknown. Since CMt has been detected in the saliva of infected cats using PCR, we hypothesised that direct transmission via social or aggressive contact may occur. The aim of this study was to evaluate this transmission route. CMt-positive saliva and blood samples were obtained from three prednisolone-treated specific pathogen-free (SPF) cats that were infected intraperitoneally with CMt. Five SPF cats were inoculated with CMt-positive saliva or blood subcutaneously to mimic cat bites, and five cats were inoculated orally with blood or oronasally with saliva to mimic social contact. Blood samples were monitored for CMt infection using quantitative real-time PCR and for seroconversion using a novel western blot assay. Neither oronasal nor subcutaneous inoculation with CMt-positive saliva led to CMt infection in the recipient cats, as determined by PCR, independent of prior prednisolone treatment. However, when blood containing the same CMt dose was given subcutaneously, 4 of the 5 cats became PCR-positive, while none of the 5 cats inoculated orally with up to 500 μL of CMt-positive blood became PCR-positive. Subsequently, the latter cats were successfully subcutaneously infected with blood. All 13 CMt-exposed cats seroconverted. In conclusion, CMt transmission by social contact seems less likely than transmission by aggressive interaction. The latter transmission may occur if the recipient cat is exposed to blood from an infected cat.     

Evaluation of fenbendazole for treatment of Giardia infection in cats concurrently infected with Cryptosporidium parvum

OBJECTIVE: To determine whether fenbendazole effectively eliminates Giardia organisms from chronically infected cats that have a concurrent Cryptosporidium parvum infection. ANIMALS: 16 clinically normal cats. PROCEDURE: Eight cats with chronic concurrent Giardia and C parvum infections received fenbendazole (50 mg/kg, PO, q 24 h) for 5 days (treatment-group cats). Feces from each cat were collected and processed 3 days weekly for 23 days after treatment. By use of an immunofluorescent assay for detection of Giardia lamblia cysts and C parvum oocysts, organism numbers were counted and scored. Fecal results from treatment-group cats were compared with those of 8 untreated cats with Giardia infection but no C parvum infection (control-group cats). RESULTS: Four of 8 treatment-group cats had consistently negative results for Giardia infection after treatment. These 4 cats had consistently positive results for C parvum oocysts prior to treatment and consistently negative results after treatment. One treatment-group cat had positive results for cysts on all fecal samples, and 3 treatment-group cats had 1 to 3 negative results and then resumed shedding large numbers of cysts; each of these cats had consistently positive results for C parvum oocysts. When compared with control-group cats, treatment-group cats shed less Giardia cysts during week 1 after treatment but not during week 2. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of fenbendazole decreases Giardia cyst shedding to less than detectable numbers in some cats. In our study, persistent C parvum infection may have been associated with failure of fenbendazole to eliminate Giardia infection.     

Prevalence of chlamydia, toxoplasma, toxocara and ringworm in farm cats in south-west England

The prevalence of infection with Chlamydia psittaci, Toxoplasma gondii, Toxocara cati and Microsporum canis was examined in 51 cats on 22 sheep farms in the Bristol area. Serum antibody to C psittaci and T gondii was present in 45 per cent and 47 per cent of cats, respectively. At the time of sampling C psittaci was isolated from 6 per cent of the cats, T cati was identified in 63 per cent of faecal samples but neither T gondii nor M canis was isolated. When examined according to the farm of origin, 22.7 per cent of farms had cat populations with no evidence of infection with C psittaci or T gondii. Of the remainder, 45.5 per cent supported cat populations with evidence of both infections and 31.8 per cent had evidence of T gondii infection alone. None of the farms had cat populations with evidence of C psittaci infection alone. Two of the cats infected with C psittaci were excreting viable organisms in the faeces. The possible significance of this to the epidemiology of ovine enzootic abortion is discussed.     

Study of feline leukemia virus immunity.

Fifteen specific-pathogen-free cats were experimentally infected with FeLV; 8 cats recovered after transient or nondetectable viremia, and 7 cats became persistently viremic. Four additional cats served as noninfected controls. Antibodies to whole FeLV (ELISA and immunoblot [western] analysis), antibodies to fixed FeLV-infected cells, and virus-neutralizing antibodies were monitored for as long as 3 years after infection. As a group, cats that recovered after acute infection developed higher titer of these various antibodies than did cats that became persistently viremic. However, specific combination or titer of antibodies was not always found in recovered cats or in persistently viremic cats. Six cats that had recovered from acute FeLV infection nearly 3 years earlier were reinfected with the same virus. Three of the cats appeared to be resistant to reinfection, 2 cats became transiently viremic, and 1 cat became persistently viremic. Slight and transient anamnestic ELISA-detectable antibody response to whole virus was seen after reinfection; immunofluorescence- and western blot-detectable responses were not greatly enhanced. Five FeLV-recovered cats were monitored for 2 years; FeLV infection spontaneously recurred in 1 cat.     

Ocular disease in FeLV-positive cats: 11 cases (1981-1986).

A total of 147 cats positive for FeLV were retrospectively studied to determine the incidence of ocular disease. Of those cats, 97 had clinical cases of the disease and 50 were artificially infected with the virus. The incidence of ocular disease among FeLV-positive cats with clinical signs of disease was less than 2%, and represented less than 0.1% of the total feline cases for the 5-year period studied. The only ocular findings that could be associated with FeLV were pupillary and motility abnormalities. Retinal hemorrhage and subsequent degeneration found in experimentally infected and naturally infected cats were secondary to profound anemia, which was secondary to FeLV infection. On the basis of the literature and our findings, FeLV is not a major cause of primary or secondary ocular disease in the cat. Anterior uveal disease (iris bombé) was detected in 1 of 147 FeLV-positive cats, and the incidence of secondary infectious disease was zero.     

Subcutaneous abscesses and arthritis caused by a probable bacterial L-form in cats

Three cats in one household developed pyogenic subcutaneous abscesses and arthritis over a period of 9.5 months. Despite vigorous surgical and antibiotic treatment, the infections in each of these cats continued to spread locally and hematogenously to involve other joints and subcutaneous sites. Although the infections did not respond to modern broad-spectrum antibiotics, they were susceptible to tetracycline. In spite of a favorable response to tetracycline, all 3 cats were euthanatized. A causative agent could not be identified by microbiologic culture of tissues obtained prior to death and at necropsy, or with special tissue stains. The infection was transmitted experimentally by sc inoculation with cell-free material from one of the naturally infected cats to a specific-pathogen-free cat. A tissue extract from the experimentally infected cat was, in turn, infectious for another specific-pathogen-free cat. The experimentally induced lesion was a rapidly enlarging necrotizing and pyogenic cellulitis and panniculitis, with no demonstrable causative agent by special tissue stains or microbiologic culture. A probable bacterial L-form was visualized in affected tissues of the experimentally infected cats and propagated in special L-form broth. Like the natural disease, infection in experimentally inoculated cats was progressive in nature, but could be treated successfully with tetracycline.