Distribution and prevalence of Cytauxzoon felis in bobcats (Lynx rufus), the natural reservoir, and other wild felids in thirteen states

Cytauxzoon felis, a protozoan parasite of wild and domestic felids, is the causative agent of cytauxzoonosis in domestic and some exotic felids in the United States. The bobcat (Lynx rufus) is the natural reservoir for this parasite, but other felids such as Florida panthers (Puma concolor coryii) and domestic cats may maintain long-term parasitemias and serve as reservoirs. Experimentally, two tick species, Dermacentor variabilis and Amblyomma americanum, have demonstrated the ability to transmit C. felis. These two tick species have overlapping distributions throughout much of the southeastern United States. The objective of the current study was to determine the distribution and prevalence of C. felis in free-ranging bobcat populations from 13 states including California, Colorado, Florida, Georgia, Kansas, Kentucky, Missouri, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, and West Virginia. These states were selected because of differential vector presence; D. variabilis is present in each of these states except for the region of Colorado sampled and A. americanum is currently known to be present only in a subset of these states. Blood or spleen samples from 696 bobcats were tested for C. felis infection by a polymerase chain reaction (PCR) assay which targeted the first ribosomal internal transcribed spacer region (ITS-1). Significantly higher prevalences of C. felis were detected from Missouri (79%, n=39), North Carolina (63%, n=8), Oklahoma (60%, n=20), South Carolina (57%, n=7), Kentucky (55%, n=74), Florida (44%, n=45), and Kansas (27%, n=41) compared with Georgia (9%, n=159), North Dakota (2.4%, n=124), Ohio (0%, n=19), West Virginia (0%, n=37), California (0%, n=26), and Colorado (0%, n=67). In addition to bobcats, seven cougars (Puma concolor) from Georgia, Louisiana, and North Dakota and one serval (Leptailurus serval) from Louisiana were tested for C. felis. Only one cougar from Louisiana was PCR positive, which represents the first report of an infected cougar outside of the Florida panther population. These data also indicate that C. felis is present in North Dakota where infection has not been reported in domestic cats. Based on a nonparametric analysis, prevalence rates were significantly higher in states where there are established populations of A. americanum, which supports recent data on the experimental transmission of C. felis by A. americanum and the fact that domestic cat clinical cases are temporally associated with A. americanum activity. Collectively, these data confirm that bobcats are a common reservoir for C. felis and that A. americanum is likely an epidemiologically important vector.     

Detection of persistent Cytauxzoon felis infection by polymerase chain reaction in three asymptomatic domestic cats

Repeated polymerase chain reaction (PCR) testing of 3 asymptomatic domestic cats were positive for Cytauxzoon felis DNA, suggesting persistent infection. Two cats initially presented with clinical signs consistent with acute cytauxzoonosis and, in both cases, signs of illness resolved after treatment. Parasitemia was detected in peripheral blood smears from these cats upon presentation with illness and, at subsequent follow-up appointments, in the absence of clinical illness. Polymerase chain reaction analysis was positive for C. felis from blood sampled at each time point. A third cat, a housemate of a cat fatally infected with C. felis, was preventatively treated for infection at the time of the housemate cat's death. This contact cat, having never shown signs of clinical illness consistent with cytauxzoonosis infection, had no detectable parasitemia but was positive for C. felis on repeated PCR testing. Detection of asymptomatically infected cats allows for the possibility of a yet unrecognized population of infected domestic cats that may have the capacity to serve as an additional reservoir host for C. felis, altering the currently accepted paradigm of C. felis transmission to domestic cats through bobcats as the reservoir host. In cases of very low parasitemia, more sensitive means of parasite detection, such as PCR testing, may be necessary to detect infected cats. Increased detection of asymptomatically infected cats will aid in understanding the epidemiology of C. felis infection and enhance the ability to prevent this highly fatal infectious disease of domestic cats.     

Cytauxzoon felis infections are present in bobcats (Lynx rufus) in a region where cytauxzoonosis is not recognized in domestic cats

This study was performed to determine the prevalence of Cytauxzoon felis (C. felis) infections in bobcats (Lynx rufus) from a region where C. felis is recognized in domestic cats, North Carolina (NC), and a region where C. felis is not recognized in domestic cats, Pennsylvania (PA). Samples from NC (n=32) were obtained post-mortem via cardiac puncture from legally trapped bobcats. Samples from PA (n=70) were collected post-mortem onto Nobuto blood collecting strips by the PA Game Commission. Each sample was tested using a C. felis specific PCR assay as well as a PCR assay targeting host DNA to rule out the presence of PCR inhibitors. Three samples were excluded due to the presence of PCR inhibitors. Thirty-three percent (10/30) of the samples from NC and 7% (5/69) of the samples from PA tested positive for the presence of C. felis. The proportion of C. felis positive bobcats from NC was significantly different than that from PA (P<0.005). Despite the lower prevalence of C. felis infections in bobcats from PA this finding is unique and indicates the potential for C. felis infections in domestic cats in the northeastern USA if the appropriate tick vectors are present. Veterinary practitioners in PA should be on alert for cytauxzoonosis in domestic cats. Further studies about the epidemiology and transmission of C. felis infections among both domestic cats and bobcats are needed.     

Characteristics of free-roaming cats and their caretakers

OBJECTIVES: To describe the characteristics of unowned, free-roaming cats and their caretakers who participated in a trap-neuter-return (TNR) program and to determine the effect of the program on free-roaming cat colonies. DESIGN: Prospective study. SAMPLE POPULATION: 101 caretakers of 920 unowned, free-roaming cats in 132 colonies in north central Florida. RESULTS: Most (85/101; 84%) caretakers were female. The median age was 45 years (range, 19 to 74 years). Most (89/101; 88%) caretakers owned pets and of those, most (67/101; 66%) owned cats. The major reasons for feeding free-roaming cats were sympathy and love of animals. Most caretakers reported that the cats they cared for were too wild to be adopted, but many also reported that they considered the cats to be like pets. The total surveyed cat population was 920 before participation in TNR and 678 after TNR. Mean colony size was 7 cats before TNR and 5.1 cats after TNR. Most cats lived on the caretaker's property. At the time of the survey, 70% (644/920) of the cats had been neutered. CONCLUSIONS AND CLINICAL RELEVANCE: The decrease in the surveyed free-roaming cat population was attributed to a reduction in births of new kittens, adoptions, deaths, and disappearances. Recognition of the human-animal bond that exists between caretakers and the feral cats they feed may facilitate the development of effective control programs for feral cat populations.     

Cytauxzoon felis infection in cats in the mid-Atlantic states: 34 cases (1998-2004)

OBJECTIVE: To describe the demographic and clinical characteristics of feline cytauxzoonosis in the mid-Atlantic states and compare the Cytauxzoon felis 18S rRNA gene sequences from affected cats with sequences reported from affected cats in other regions. DESIGN: Retrospective case series. ANIMALS: 34 cats with C. felis infection. PROCEDURE: Medical records of cats in which C. felis infection was diagnosed from May 1998 through June 2004 were reviewed; data collected included signalment, month of diagnosis, geographic location, clinicopathologic abnormalities, medical treatments, outcome, and necropsy findings when applicable. Cytauxzoon felis DNA was amplified, cloned, and sequenced from 4 of these cats and compared with previously reported C. felis DNA sequences. RESULTS: Of 34 C. felis-infected cats, 28 resided in North Carolina, 3 resided in South Carolina, and 3 resided in Virginia; in 32 cats, a diagnosis of C. felis infection was made in April through September. Pancytopenia and icterus were the most common clinicopathologic abnormalities. Thirty-two cats either died or were euthanatized, and 2 cats survived. At 5 veterinary hospitals, multiple cases were identified, and 4 multicat households had > 1 cat infected with C. felis. The 18S rRNA gene sequences characterized in organisms obtained from 4 cats were nearly identical to C. felis DNA sequences reported from other US regions. CONCLUSIONS AND CLINICAL RELEVANCE: Data indicate that veterinarians in the mid-Atlantic region of the United States should consider C. felis infection in cats that become ill with fever, icterus, and pancytopenia or bicytopenia, especially in the spring and summer months.     

Use of matrix population models to estimate the efficacy of euthanasia versus trap-neuter-return for management of free-roaming cats

OBJECTIVE: To evaluate the efficacy of trap-neuter-return and trap-euthanatize management strategies for controlling urban free-roaming cat populations by use of matrix population models. DESIGN: Prospective study. SAMPLE POPULATION: Estimates of free-roaming cat populations in urban environments. PROCEDURE: Data from the literature describing the biology of free-roaming cat populations in urban environments were gathered. A matrix population model was developed with a range of high and low survival and fecundity values and all combinations of those values. The response of population growth rate to a range of management actions was assessed with an elasticity analysis. RESULTS: All possible combinations of survival and fecundity values of free-roaming cats led to predictions of rapid, exponential population growth. The model predicted effective cat population control by use of annual euthanasia of > or = 50% of the population or by annual neutering of > 75% of the fertile population. Elasticity analyses revealed that the modeled population was most susceptible to control through euthanasia. CONCLUSIONS AND CLINICAL RELEVANCE: Free-roaming cat populations have a high intrinsic growth rate, and euthanasia is estimated to be more effective at reducing cat populations than trap-neuter-return programs.     

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.     

Prevalence of feline leukaemia virus and antibodies to feline immunodeficiency virus in cats in the United Kingdom

A representative sample of the pet cat population of the United Kingdom was surveyed. Blood samples from 1204 sick and 1007 healthy cats of known breed, age and sex were tested for antibodies to feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). The prevalence of FIV was 19 per cent in sick cats and 6 per cent in healthy cats, and the prevalence of FeLV was 18 per cent in sick cats and 5 per cent in healthy cats; both infections were more common in domestic cats than in pedigree cats. Feline immunodeficiency virus was more prevalent in older cats but FeLV was more prevalent in younger cats. There was no difference between the prevalence of FeLV in male and female cats but male cats were more likely to be infected with FIV than female cats. No interaction was demonstrated between FIV and FeLV infections. Of the cats which were in contact with FIV in households with more than one cat, 21 per cent had seroconverted. The prevalence of FeLV viraemia in cats in contact with FeLV was 14 per cent. The clinical signs associated with FIV were pyrexia, gingivitis/stomatitis and respiratory signs, and with FeLV, pyrexia and anaemia. It was concluded that both viruses were significant causes of disease, and that the cats most likely to be infected with FIV were older, free-roaming male cats and for FeLV, younger, free-roaming cats.     

Experimental infection of domestic cats (Felis domesticus) with Cytauxzoon manul from Pallas' cats (Otocolobus manul)

In a random, blind study, six domestic cats were assigned to two treatment groups that received either sterile water or dexamethasone by subcutaneous injection prior to intravenous inoculation with Pallas' cat (Otocolobus manul) blood infected with Cytauxzoon manul. A seventh domestic cat served as a control and was inoculated only with sterile water. Cats were monitored for clinical signs consistent with cytauxzoonosis, and periodically screened for hemoparasitemia. All domestic cats (6/6) that received Pallas' cat blood infected with C. manul developed a low but detectible parasitemia by 9 days post-inoculation, yet remained clinically healthy. All domestic cats (7/7) were subsequently challenged with Cytauxzoon felis and developed clinical signs typical of cytauxzoonosis within 5 days post-challenge. Affected animals were euthanized and cytauxzoonosis was confirmed by histopathology. While inoculation of domestic cats with Pallas' cat blood infected with C. manul induced a parasitemia, it did not cause disease or provide protection against challenge with C. felis. Further studies are warranted to determine the potential for interspecies transmission and disease with C. manul.     

Number of unowned free-roaming cats in a college community in the southern United States and characteristics of community residents who feed them

OBJECTIVE: To estimate the number of unowned free-roaming cats in a college community in the southern United States and identify the characteristics of community residents who feed these cats. DESIGN: Cross-sectional, random-digit telephone survey. SAMPLE POPULATION: 587 households in Alachua County, Florida, surveyed between March 1 and May 10, 1999. PROCEDURE: Telephone surveys were conducted, and respondents were asked questions about feeding of unowned free-roaming cats. RESULTS: 70 (12%) households fed free-roaming cats; mean +/- SD number of free-roaming cats fed per household was 3.6 +/- 1.9. Households that fed free-roaming cats were more likely to own pet cats than were households that did not feed free-roaming cats; however, 30 of 70 (43%) households feeding free-roaming cats did not own cats or dogs. Although the percentage of pet cats that were neutered was high (90%), only 8 (11%) households that fed free-roaming cats attempted to have such cats neutered. The free-roaming cat population was estimated to represent approximately 44% of the population of cats in the county. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that unowned free-roaming cats may represent a substantial portion of the total cat population in a region. Public policies and education programs aimed at reducing cat overpopulation should include provisions for neutering unowned free-roaming cats, and efforts should target the general public, not only pet owners, because not all households that feed unowned free-roaming cats own pets.     

Molecular detection and characterization of Haemobartonella felis in domestic cats in Japan employing sequence-specific polymerase chain reaction (SS-PCR)

A novel PCR assay was developed in order to examine the prevalence of Haemobartonella felis (H. felis) in Japanese domestic cats and which was able to differentiate of the Ohio strain and the California strain of H. felis. Blood samples from a total of 21 cats suspected of having haemobartonellosis were examined employing a novel PCR assay and demonstrated positive results in 18 cats which was confirmed by cytological examination of blood smears. Four out of 18 positive cats (22%) were infected with the California strain, whilst the other 12 cats (67%) were infected with the Ohio strain and two animals (11%) were infected with both strains. As most of the cats with moderate to severe anemia were infected with the Ohio strain, it is suggested that the most prevalent strain of H. felis in Japanese domestic cats might be the Ohio strain. In the present study, it was thought that molecular detection and characterization of H. felis may provide valuable information regarding the severity and prognosis of this illness.     

Analysis of the impact of trap-neuter-return programs on populations of feral cats

OBJECTIVE: To evaluate 2 county trap-neuter-return (TNR) programs for feral cat population management via mathematical modeling. DESIGN: Theoretical population model. ANIMALS: Feral cats assessed from 1992 to 2003 in San Diego County, California (n = 14,452), and from 1998 to 2004 in Alachua County, Florida (11,822). PROCEDURE: Data were analyzed with a mathematical Ricker model to describe population dynamics of the feral cats and modifications to the dynamics that occurred as a result of the TNR programs. RESULTS: In both counties, results of analyses did not indicate a consistent reduction in per capita growth, the population multiplier, or the proportion of female cats that were pregnant. CONCLUSIONS AND CLINICAL RELEVANCE: Success of feral cat management programs that use TNR can be monitored with an easily collected set of data and statistical analyses facilitated by population modeling techniques. Results may be used to suggest possible future monitoring and modification of TNR programs, which could result in greater success controlling and reducing feral cat populations.     

城市流浪犬猫的成因、危害与对策

根据城市流浪犬猫的成因与危害,提出慎养、绝育、收容收养、捕捉一绝育一放归等控制流浪犬猫数量的方法。解决流浪犬猫问题的关键在于从源头上减少流浪犬猫的数量,为此,科学地传播爱护动物与尊重生命的意义是极为重要的。     

Evaluation of the effect of a long-term trap-neuter-return and adoption program on a free-roaming cat population

OBJECTIVE: To evaluate the effect of a long-term trap-neuter-return program, with adoption whenever possible, on the dynamics of a free-roaming cat population. DESIGN: Observational epidemiologic study. ANIMALS: 155 unowned free-roaming cats. PROCEDURES: Free-roaming cats residing on a university campus were trapped, neutered, and returned to the environment or adopted over an 11-year period. RESULTS: During the observation period (January 1991 to April 2002), 75% of the cats were feral, and 25% were socialized. Kittens comprised 56% of the original population. Male cats were slightly more numerous (55%) than females. At the conclusion of the observation period, 47% of the cats had been removed for adoption, 15% remained on site, 15% had disappeared, 11% were euthanatized, 6% had died, and 6% had moved to the surrounding wooded environment. Trapping began in 1991; however, a complete census of cats was not completed until 1996, at which time 68 cats resided on site. At completion of the study in 2002, the population had decreased by 66%, from 68 to 23 cats (of which 22 were feral). No kittens were observed on site after 1995, but additional stray or abandoned cats continued to become resident. New arrivals were neutered or adopted before they could reproduce. CONCLUSIONS AND CLINICAL RELEVANCE: A comprehensive long-term program of neutering followed by adoption or return to the resident colony can result in reduction of free-roaming cat populations in urban areas.     

An etiological investigation of domestic cats with conjunctivitis and upper respiratory tract disease in Japan

Chlamydophila felis (C. felis), feline herpesvirus-1 (FHV-1) and feline calicivirus (FCV) were detected in 39 (59.1%), 11 (16.7%) and 14 (21.2%) cats respectively, from 66 domestic cats presented with conjunctivitis and upper respiratory tract disease (URTD) in 9 prefectures of Japan. Dual and multiple infections were found in 7 (10.6%) cats with both C. felis and FHV-1, 10 (15.2%) cats with both C. felis and FCV, and 1 (1.5%) cat with all three agents. C. felis was isolated from 11 (28.2%) of 39 PCR positive cats. Antigenic difference was found in a 96 kDa protein of our isolates and Fe/145 strain isolated in USA. In conclusion, C. felis is the most common agent of feline conjunctivitis and URTD, and the coinfection with C. felis, FHV-1 and FCV are also common in cats in Japan.     

Characteristics of free-roaming cats evaluated in a trap-neuter-return program

OBJECTIVE: To determine characteristics of free-roaming cats evaluated in a trap-neuter-return program. DESIGN: Cross-sectional study. ANIMALS: 5,323 free-roaming cats. PROCEDURE: Data collected included sex, maturity, pregnancy status, number of fetuses per pregnancy, cryptorchidism, and occurrence of complications or euthanasia. RESULTS: Adult cats represented 85% of the population, and 57% were female. Overall, 19% of adult females were pregnant, and mean litter size was 3.6 fetuses. Pregnancy rate peaked at 36 to 47% of all females evaluated in March and April and decreased to < or = 4% from October through January. Cryptorchidism was observed in 1.9% of the males; 0.4% of the adult females had pyometra. Only 1.9% of the cats were already neutered. Euthanasia and unexpected death rates were 0.4 and 0.3%, respectively. The most common severe problems encountered included pyometra, neoplasia, surgical complications, diaphragmatic hernia, debilitation, and chronic inflammatory diseases. CONCLUSIONS AND CLINICAL RELEVANCE: Neutering programs for free-roaming cats should include preparations to perform more spays than castrations. Typically, almost half of the female cats trapped during spring will be pregnant. Cryptorchidism is uncommon but is encountered on a consistent basis, so care should be taken to differentiate previous castration from retained testicles. Euthanasia of debilitated cats for humane reasons is rarely necessary, and unexpected deaths occur at a low rate. It is feasible and safe to neuter large numbers of free-roaming cats in large-scale clinics.     

Detection of Cryptosporidium felis and Giardia duodenalis Assemblage F in a cat colony

Eighteen cats, 3-6 months of age, bred and housed in a closed colony, were transferred from that colony and placed in separate stainless steel cages in a building designed for housing animals. At daily intervals, feces were collected from the litter pans in each cage, pans and cages were cleaned, and fresh food and water were provided. Beginning 4 weeks after the transfer, oocysts of Cryptosporidium were detected in the feces of two cats by brightfield microscopy. For the following 21 days, with minor exceptions, feces from each cat were collected daily and examined by immunofluorescence microscopy and by molecular methods that included DNA extraction, 18S rDNA gene amplification, and DNA sequence analysis. Within those 22 days, every cat was found to be infected with Cryptosporidium felis and excreted oocysts for 6-18 days. Eight of these 18 cats also excreted cysts of Giardia duodenalis Assemblage F, a genotype found only in cats. Six Giardia infections were concurrent during part of the patency with C. felis infections. Neither diarrhea nor other signs of illness were observed in any of the cats during this time. Because C. felis is zoonotic these findings suggest that care should be taken by veterinary health care providers and others in close contact with cats, even when cats appear healthy and asymptomatic.     

Treatment of experimentally induced cytauxzoonosis in cats with parvaquone and buparvaquone

The efficacy of parvaquone (Clexon) and buparvaquone (Butalex) in treating experimentally induced feline cytauxzoonosis was explored. Domestic cats were inoculated subcutaneously with blood from a cat infected with Cytauxzoon felis and treated daily with either 20 or 30 mg kg-1 parvaquone, or 5 or 10 mg kg-1 buparvaquone, beginning on either the first day parasites were detected in peripheral blood, or 2 days after the onset of parasitemia. Fifteen cats were treated and all but one died due to the infection. Unexpectedly, one of two non-treated, infected control cats survived. Although parvaquone and buparvaquone are the treatments of choice for a related hemoprotozoan parasite causing theileriosis in African cattle, wer concluded that at the dosages and regimes tested, these drugs are not effective treatments for feline cytauxzoonosis. Blood from the two surviving cats was inoculated into naive cats and in these animals clinical disease or death were not observed. The latter two naive recipient cats were then inoculated with a lethal dose of viable, frozen C. felis and both died, thereby indicating that blood from surviving cats did not induce an infectious state that resulted in immunity. The two cats that survived the acute infection were subsequently challenged with a lethal inoculum of C. felis; they showed no clinical signs of cytauxzoonosis and were obviously immune to reinfection.     

Cats surviving natural infection with Cytauxzoon felis: 18 cases (1997-1998)

Eighteen cats surviving natural infection with Cytauxzoon felis were identified. All cats came from a limited geographic area in northwestern Arkansas and northeastern Oklahoma. Clinical signs in most cats were similar to those described for cytauxzoonosis; however, 4 cats were asymptomatic. All cases were initially diagnosed by microscopic identification of signet ring-shaped piroplasms in erythrocytes of peripheral blood smears. Four of 4 cats tested had detectable serum antibodies to C felis. Four different cats were positive by polymerase chain reaction (PCR). Partial sequencing of the PCR product from 1 cat revealed >99% homology with the reported sequence of C felis. Repeated examination of blood smears from 12 cats revealed that the erythroparasitemia was generally persistent for the duration of follow-up (3-154 days). Survival did not seem dependent on treatment, as only 1 cat was treated with a drug with potential antiprotozoal activity (imidocarb dipropionate), and 4 cats received no treatment. The findings of this study may indicate the existence of a less virulent strain of C felis.     

Reproductive capacity of free-roaming domestic cats and kitten survival rate

OBJECTIVE: To determine reproductive capacity of naturally breeding free-roaming domestic cats and kitten survival rate. DESIGN: Prospective cohort and retrospective cross-sectional study. ANIMALS: 2,332 female cats brought to a trap-neuter-return clinic for neutering and 71 female cats and 171 kittens comprising 50 litters from a cohort study of feral cats in managed colonies. PROCEDURE: Data collected for all cats included pregnancy, lactation, and estrus status and number of fetuses for pregnant cats. Additional data collected for feral cats in managed colonies included numbers of litters per year and kittens per litter, date of birth, kitten survival rate, and causes of death. RESULTS: Pregnant cats were observed in all months of the year, but the percentage of cats found to be pregnant was highest in March, April, and May. Cats produced a mean of 1.4 litters/y, with a median of 3 kittens/litter (range, 1 to 6). Overall, 127 of 169 (75%) kittens died or disappeared before 6 months of age. Trauma was the most common cause of death. CONCLUSIONS AND CLINICAL RELEVANCE: Results illustrate the high reproductive capacity of free-roaming domestic cats. Realistic estimates of the reproductive capacity of female cats may be useful in assessing the effectiveness of population control strategies.