Characterizing clinics involved in controlling stray cats

D'Ávila, A. M. E. D. (2016). Caracterização dos Centros de Atendimento Médico-Veterinários no Concelho de Lisboa que participam no controlo da população de gatos errantes e assilvestrados. Universidade Lusófona de Humanidades e Tecnologias. Faculdade de Medicina Veterinária

The presence of stray and feral cats in urban areas often leads to situations of overpopulation whereby the control of reproduction has proven to be a priority element in solving this problem. The primary goal of this study was to characterize the clinics in the Lisbon area in controlling the population of stray cats and to determine their impact on reducing the number of animals. To accomplish this, it has been developed a questionnaire submitted to clinical directors. Of the 44 participants, it was found that 52% participates in population control programs. The secondary goals were to evaluate protocols applied in relation to neutering and it was verified that most procedures performed in these cases follow the recommendations made by the specialized agencies, including the type of surgery (95,6% neuter and 100% spay), preanesthetic protocols, performing surgeries in pregnant cats (91,3% perform against 8,7% that does not perform), the use of nonsteroidal anti-inflammatory drugs (91% use them against 9% that does not use them), the use of fluidtherapy (65% use it against 35% that does not use it), the location of the postoperative period, the FIV-FeLV testing (78,26% does not test against 21,74% that does test) and the practice of left ear-cutting (86,96% cut against 13,04% that does not cut). On the contrary, performing sterilization on pre-pubertal cats is not followed (only 21,7% on males and 34,8% on females neuter before 6 months of age) and the use of antibiotics by the clinical staff is considered excessive (91% use them against 9% that does not use them) to the recommended parameters. In addition, using likelihood ratios established in the literature, it was also determined that the 2538 surgeries performed annually by this sample, prevent the birth of 6396 kittens and the wandering of 1599 cats, demonstrating the important role of clinics in fighting overpopulation of stray cats in Lisbon.

FeLV and FIV in free-roeaming cats

Lee, I.T., Levy, J.K., Gorman, S.P., Crawford, P.C. and Slater, M.R.2002. Prevalence of feline leukemia virus infection and serum antibodies against feline immunodeficiency virus in un-owned free-roaming cats. Journal of the American Veterinary Medical Association, 220: 620–622.

Objective—To determine prevalence of FeLV infection and serum antibodies against feline immunodeficiency virus (FIV) in unowned free-roaming cats.
Design—Cross-sectional serologic survey.
Animals—733 unowned free-roaming cats in Raleigh, NC, and 1,143 unowned free-roaming cats in
Gainesville, Fla.
Results—In Raleigh, overall prevalence of FeLV infection was 5.3%, and overall seroprevalence for FIV was 2.3%. In Gainesville, overall prevalence of FeLV infection was 3.7%, and overall seroprevalence for FIV was 4.3%. Overall, FeLV prevalence was 4.3%, and seroprevalence for FIV was 3.5%. Prevalence of FeLV infection was not significantly different between males (4.9%) and females (3.8%), although seroprevalence for FIV was significantly higher in male cats (6.3%) than in female cats (1.5%).
Conclusions and Clinical Relevance—Prevalence of FeLV infection and seroprevalence for FIV in unowned free-roaming cats in Raleigh and Gainesville are similar to prevalence rates reported for owned cats in the United States. Male cats are at increased risk for exposure to FIV, compared with female cats.

Patterns of seroprevalence of feline viruses among domestic cats and Pallas’ cats

Pavlova, E. V., Kirilyuk, V. E., & Naidenko, S. V. (2015). Patterns of seroprevalence of feline viruses among domestic cats (Felis catus) and Pallas’ cats (Otocolobus manul) in Daursky Reserve, Russia. Canadian Journal of Zoology, 93(11), 849-855.

Few data are available on the prevalence of feline viruses in the wild and little is known about natural sources of infections. The aim of this study was to estimate patterns of seroprevalence to feline viruses (feline immunodeficiency virus (FIV), feline calicivirus (FCV), feline panleukopenia virus (FPV), feline herpesvirus (FHV), and feline leukemia virus (FeLV)) in two cat species, domestic cats (Felis catus L., 1758) (n = 61) and Pallas’ cats (Otocolobus manul (Pallas, 1776)) (n = 24), living in the same area, in Daursky Reserve, Russia. Our results indicate that four of five viruses are circulating in the study area, with the exception of FHV. The pattern of FCV and FPV prevalence differed from FIV and FeLV. FCV and FPV seroprevalence did not depend on the sex and predominated in the group of cats living in the village (76% and 55%, respectively). No Pallas’ cats were seropositive to these viruses. The prevalence of FIV and FeLV were similar in areas with different cat densities (at the stations (16% for both viruses) and in the village (16% for both viruses)). The patterns of seroprevalence between species testify to the low rate of interspecific contacts. In Pallas’ cats, we found the presence of antibodies to FIV to be 5% and antigens of FeLV to be 5%, pathogens for which transmission demand close direct contacts between animals (mainly aggressive and (or) sexual contact), which is typical in the breeding season. Arid climate may also reduce patterns of viral prevalence in the study area, decreasing the risk of infection for both cat species.

Epidemiology of FeLV and FIV in USA and Canada

Chhetri, B. (2015). Spatial and temporal epidemiology of feline immunodeficiency virus and feline leukemia virus infections in the United States and Canada (Doctoral dissertation, The University of Guelph).

This thesis investigates the geographical and temporal variations in feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) infections, and the importance of known risk factors for these infections relative to each other in the United States and Canada. In addition, the effect of the modifiable areal unit problem (MAUP) on commonly used spatial analysis methods was assessed.
Choropleth mapping and spatial scan testing revealed that compared to FIV, FeLV infection was predominant in western regions, and FIV infection was predominant in eastern regions of the US. A multilevel case-case study design for comparison of FIV and FeLV infections indicated that cats that were adult, male, healthy, or outdoor cats were more likely to be seropositive for FIV compared to FeLV when compared to juvenile, female, sick or cats kept exclusively indoors. Neuter status and testing at clinic or shelter did not differ significantly between the two infections. Time series analysis did not reveal an increasing or decreasing trend in FIV or FeLV seropositivity among cats tested at the Animal Health Laboratory (AHL) from 1999-2012. Further, the FIV vaccine introduction did not have a significant effect on changing seroprevalence for FIV. It was evident from this study that commonly used spatial epidemiological methods (Moran's I, the spatial scan test and spatial Poisson regression modeling) are sensitive to the choice of the spatial aggregation scale (state, county, postal code levels) for analysis, (i.e., are affected by the MAUP). The MAUP effect was expressed as differences in strength and significance of clustering, differences in size and number of clusters detected, and differences in significance and magnitude of associations between FIV or FeLV infections and predictor variables as the level of aggregation changed.

A survey of feline leukaemia virus infection of domestic cats from selected areas in Harare

Muchaamba, F., Mutiringindi, T. H., Tivapasi, M. T., Dhliwayo, S., & Matope, G. (2014). A survey of feline leukaemia virus infection of domestic cats from selected areas in Harare, Zimbabwe. Journal of the South African Veterinary Association, 85(1), 6-pages.

A cross-sectional study was conducted to detect the feline leukaemia virus (FeLV) p27 antigen and to determine risk factors and the haematological changes associated with infection in domestic cats in Zimbabwe. Sera were collected for detection of the p27 antigen, urea, creatinine, alanine aminotransferase and gamma-glutamyl transferase levels, whilst whole blood was collected for haematology. FeLV p27 antigen was detected using a rapid enzyme-linked immunosorbent assay (ELISA) test kit. Data on risk factors were analysed using a logistic regression model. Of the 100 cats tested, 41% (95% CI: 31.19% - 50.81%) (41/100) were positive for the FeLV p27 antigen. Sex and health status of cats were not significantly (p > 0.05) associated with infection. Intact cats (OR = 9.73), those living in multicat housing (OR = 5.23) and cats that had access to outdoor life (OR = 35.5) were found to have higher odds of infection compared with neutered cats, those living in single-cat housing, and without access to outdoor life, respectively. Biochemistry and haematology revealed no specific changes. The results showed that FeLV infection was high in sampled cats, providing evidence of active infection. Thus, it would be prudent to introduce specific control measures for FeLV infection in Zimbabwe.

FIV and FeLV in native and stray felines

Mora, M., Napolitano, C., Ortega, R., Poulin, E., & Pizarro-Lucero, J. (2014). Feline immunodeficiency virus and feline leukemia virus infection in free-ranging guignas (Leopardus guigna) and sympatric domestic cats in human perturbed landscapes on Chiloé island, Chile. Journal of Wildlife Diseases.

Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are two of the most common viruses affecting domestic cats (Felis catus). During the last two decades, reports show that both viruses also infect or affect other species of the family Felidae. Human landscape perturbation is one of the main causes of emerging diseases in wild animals, facilitating contact and transmission of pathogens between domestic and wild animals. We investigated FIV and FeLV infection in free-ranging guignas (Leopardus guigna) and sympatric domestic cats in human perturbed landscapes on Chiloé Island, Chile. Samples from 78 domestic cats and 15 guignas were collected from 2008 to 2010 and analyzed by PCR amplification and sequencing. Two guignas and two domestic cats were positive for FIV; three guignas and 26 domestic cats were positive for FeLV. The high percentage of nucleotide identity of FIV and FeLV sequences from both species suggests possible interspecies transmission of viruses, facilitated by increased contact probability through human invasion into natural habitats, fragmentation of guigna habitat, and poultry attacks by guignas. This study enhances our knowledge on the transmission of pathogens from domestic to wild animals in the global scenario of human landscape perturbation and emerging diseases.

Reducing feral cat threats to native wildlife in Hawai`i

Hess, S. C., H. Hansen, and P. C. Banko. 2007. Reducing feral cat threats to native wildlife in Hawai`i. Hawai`i Cooperative Studies Unit Technical Report HCSU-010. University of Hawai`i at Hilo. 102 pp., incl. 14 figures, & 19 tables.

We documented the diet of feral cats (Felis catus) on Kīlauea and Mauna Loa within Hawai`i Volcanoes National Park (HAVO), determined the incidence of three feline diseases on Mauna Kea, studied feral cat home range, developed and tested trap-signaling devices, tested food-based baits and attractants, analyzed feral cat population dynamics using genetic techniques, and developed an adaptive strategy for reducing predation on endangered Hawaiian birds.

We documented the diet of feral cats by analyzing the contents of 42 digestive tracts from Kīlauea and Mauna Loa in Hawai`i Volcanoes National Park. Small mammals, invertebrates, and birds were the most common prey types consumed by feral cats. Birds occurred in 27.8–29.2% of digestive tracts. The total number of bird, small mammal, and invertebrate prey differed between Kīlauea and Mauna Loa. On Mauna Loa, significantly more (89%) feral cats consumed small mammals, primarily rodents, than on Kīlauea Volcano (50%). Mice (Mus musculus) were the major component of the feral cat diet on Mauna Loa, whereas Orthoptera were the major component of the diet on Kīlauea. We recovered a mandible set, feathers, and bones of an endangered Hawaiian Petrel (Pterodroma sandwichensis) from a digestive tract from Mauna Loa. This specimen represents the first well-documented endangered seabird to be recovered from the digestive tract of a feral cat in Hawai`i and suggests that feral cats prey on this species.

We determined prevalence to feline immunodeficiency virus (FIV) antibodies, feline leukemia virus (FeLV) antigen, and Toxoplasma gondii antibodies in feral cats on Mauna Kea Hawai`i from April 2002 to May 2004. Six of 68 (8.8%) and 11/68 (16.2%) were antibody positive to FIV and antigen positive for FeLV, respectively; 25/67 (37.3%) were seropositive to T. gondii. Antibodies to FeLV and T. gondii occurred in all age and sex classes, but FIV occurred only in adult males. Evidence of previous or current infections with two of these infectious agents was detected in eight of 64 cats (12.5%). Despite exposure to these infectious agents, feral cats remain abundant throughout the Hawaiian Islands.

Feral cats in dry subalpine woodland of Mauna Kea, Hawai`i, live in low density and exhibit some of the largest reported home ranges in the literature. While 95% fixed kernel home range estimates for three females averaged 772 ha, four males averaged 1,418 ha, and one male maintained a home range of 2,050 ha. Mean daily movement rates between sexes overlapped widely and did not differ significantly (P = 0.083). Log-transformed 95% kernel home ranges for males were significantly larger than those of females (P = 0.024), but 25% kernel home ranges for females were larger than those of males (P = 0.017). Moreover, logtransformed home ranges of males were also significantly larger than those of females in this and seven other studies from the Pacific region (P = 0.044). Feral cats present a major threat to endangered Hawaiian birds, but knowledge of their ecology can be used for management by optimizing trap spacing and creating buffer zones around conservation areas.

Frequent checks of live traps require enormous amounts of labor and add human scents associated with repeated monitoring which may reduce capture efficiency. To reduce efforts and increase efficiency, we developed a trap-signaling device with long-distance reception, durability in adverse weather, and ease of transport, deployment, and use. Modifications from previous designs include a normally-open magnetic switch and a mounting configuration to maximize reception. The system weighed < 225 g, was effective ≤ 17.1 km, and failed in < 1% of trap-nights. Employing this system, researchers and wildlife managers may reduce the amount of effort checking traps while improving the welfare of trapped animals.

Successful feral cat control programs require effective baits and lures. Non-targets may interfere with trapping efforts by rapidly consuming bait before feral cats encounter traps, necessitating frequent bait replacement. We compared the effectiveness of baits and lures by analyzing capture rates of feral cats and non-targets and monitoring animal visits to bait stations with remotely-triggered cameras. We tested four different baits and attractants: canned cat food, sardines, catnip, and a bait sausage that we formulated from pork and fat. We trapped for a total of 3,389 trap nights and captured 35 feral cats. There were 323 incidences of trap interferences, reducing the effective trap nights (ETN) to 3,225. The primary cause of trap interference was feral pigs rolling over traps (n = 185, 57.3% of interferences). The primary non-target species captured were small Indian mongooses (n = 74, 22.9% of interferences). Overall, more cats and mongooses were captured using sardines, although the catch frequencies were not dependent on the bait type used. We obtained photographs of 1,476 small mammals at the bait stations. Mongooses were the principal mammals photographed (n = 939, 69.5% of pictures). We also obtained 398 photographs of rats (29.5%) and 9 (0.7%) of mice. Feral cats were photographed only 5 (0.4%) times. We found strong differences between mongooses, rodents, and cats photographed at the four bait types. Sardines were the most visited bait type (n = 641, 47.4% of photographs). Pork sausage and cat food accounted for 383 (28.3%) and 322 (23.8%) visits while catnip had only 67 (5.0%) visits. Feral cats were photographed only at sardine bait. Mongooses were attracted primarily to  sardines (49.3%). Pork sausage was the most attractive bait to rats, accounting for 44.5% of photographs. Due to the high rate of non-target interference, other attractants need to be tested for successful feral cat control programs.

Population genetics can provide information about the demographics and dynamics of invasive species that is beneficial for developing effective control strategies. We studied the population genetics of feral cats on Hawai`i Island by microsatellite analysis to evaluate genetic diversity and population structure, assess gene flow and connectivity among three populations, identify potential source populations, characterize population dynamics, and evaluate sex-biased dispersal. High genetic diversity, low structure, and high number of migrants per generation supported high gene flow that was not limited spatially. Migration rates revealed that most migration occurred out of West Mauna Kea. Effective population size estimates indicated increasing cat populations despite control efforts. Despite high gene flow, relatedness estimates declined significantly with increased geographic distance and Bayesian assignment tests revealed the presence of three population clusters. Genetic structure and relatedness estimates indicated male-biased dispersal. Mauna Kea may be a source population that can be targeted for control. However, recolonization seems likely given the great dispersal ability that may not be inhibited by barriers such as lava flows. Genetic monitoring will be necessary to assess the effectiveness of future control efforts.

Despite the long history of feral cats in Hawai`i, there has been little research to provide strategies to improve control programs and reduce depredation on endangered species. Our objective was to develop a predictive model to determine how landscape features on Mauna Kea such as habitat, elevation, and proximity to roads affect the number of feral cats captured at each trap. We used log-link generalized linear models and QAICc model ranking criteria to determine the effect of these factors. We found that the number of cats captured per trap was related to trapping effort, habitat type, and whether traps were located on the West or North Slope of Mauna Kea. We recommend an adaptive management strategy to minimize trapping interference by non-target small Indian mongoose (Herpestes auropunctatus) with toxicants, to focus trapping efforts in māmane (Sophora chrysophylla) habitat on the West slope of Mauna Kea, and to cluster traps near others that have previously captured multiple cats.

Modelling biological control of cat populations

Courchamp, F. & G. Sugihara. 1999. Modelling biological control of alien predator populations to protect native island prey species from extinction. Ecological Applications, 9: 112-123.

Introduced feral cat (Felis catus) populations are an important threat to many island vertebrate populations and to bird species in particular. Elimination of feral cat populations is desirable in most of these ecosystems. Release of a parasite species in these mostly immune-naive populations is thought to be an efficient eradication measure. Such an approach is theoretically investigated here, using a mathematical model that describes the effects of introducing a virus into the cat population on population dynamics of both the cat and its prey. We studied the effects of two types of introduced feline viruses: Feline Immunodeficiency Virus and Feline Leukemia Virus, both of which are good candidates for eradicating a cat population. Results show that eradication is possible with Feline Leukemia Virus, if natural immunity is sufficiently low. Feline Immunodeficiency Virus cannot fully eradicate cat populations, but can be an effective agent for long-term control of cat populations on islands where total cat eradication is not possible (e.g., there is a high likelihood of continued introduction of cats) or not desirable (e.g., when rats are present). Culling, which by itself would require a very prolonged and logistically demanding effort to eliminate cat populations, may be more efficient when applied simultaneously with virus introduction.

Impact of two feline retroviruses on natural populations of domestic cat

Courchamp, F., D. Pontier, E. Fromont & M. Artois. 1995. Impact of two feline retroviruses on natural populations of domestic cat. Mammalia. 59 (4): 589-598.

We compared the pattern of spread and the impact of two retroviruses, feline immunodeficiency
virus (FIV), and feline leukemia (FeLV) within natural populations of domestic. A four years epidemiological study shows that FIV is present in three studied rural cat populations, whereas FeLV is absent in one out of the three, with no evolution in time for either virus. Factros influencing FIV transmission are directly linked to agressive behaviour , while factors influencing FeLV transmission are rather characteristic of amicable interactions. Results of a deterministic model show that both infections are maintained in the population at a stable equilibrium between susceptible and infected animals, slightly reduce the number of individuals at equilibrium, and have long transmission rates. Results of a long term dynamical study indicate that the probability of dying from tese viruses is low in natural conditions, and that, despite their presence, the size and structure of the population remains stable.
In conclusion, despite FIV and FeLV have different spread patterns (FIV infects and kills at-risk individuals, while FeLV infects more indiscriminately), the impact of both retroviruses on cat populations seems to be low. 

Infection strategies of retroviruses to control feral cats

Fromont, E., Courchamp, F., Pontier, D., & Artois, M. (1997). Infection strategies of retroviruses and social grouping of domestic cats. Canadian journal of zoology, 75(12), 1994-2002.

It is thought that parasites may exert selective pressure on the social structure of host populations. We compared the impact of feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV), two retroviruses commonly found in domestic cats (Felis catus). Because of low transmissibility and virulence, both infections have a worldwide distribution and low prevalence. Transmission modes differ: FIV is transmitted only through biting, while FeLV transmission occurs by biting, licking, grooming, and sharing food and from mother to fetus. FeLV is also more pathogenic than FIV. We compared FIV and FeLV prevalence and risk factors within five populations of cats. FIV infection occurred almost exclusively among adult male cats fighting to acquire and maintain dominant status. Classes at risk for FeLV infection included sexually intact cats allowed to roam freely. The impact of FeLV on host population growth was greater than that of FIV but varied among populations. Our results show that FIV is favoured by individual aggressiveness and a hierarchical social system, while FeLV is more prevalent among socially active cats. FeLV may constitute a source of selective pressure against numerous amicable contacts, particularly in urban cat populations, where aggression among individuals is reduced.

Feral cat vaccination and TNR

Fischer, S.M., C.M. Quest, E. J. Dubovi, R. D. Davis, S.J. Tucker, J.A. Friary, P.C. Crawford, T. A. Ricke, & J.K. Levy. (2007) Response of feral cats to vaccination at the time of neutering. Journal of the American Veterinary Medical Association 230 (1): 52-58

Objective—To determine whether administration of inactivated virus or modified-live virus (MLV) vaccines to feral cats at the time of neutering induces protective serum antiviral antibody titers.

Design—Prospective study.

Animals—61 feral cats included in a trap-neuter-return program in Florida.

Procedures—Each cat received vaccines against feline panleukopenia virus (FPV), feline herpes virus (FHV), feline calicivirus (FCV), FeLV, and rabies virus (RV). Immediately on completion of surgery, vaccines that contained inactivated RV and FeLV antigens and either MLV or inactivated FPV, FHV, and FCV antigens were administered. Titers of antiviral antibodies (except those against FeLV) were assessed in serum samples obtained immediately prior to surgery and approximately 10 weeks later.

Results—Prior to vaccination, some of the cats had protective serum antibody titers against FPV (33%), FHV (21%), FCV (64%), and RV (3%). Following vaccination, the overall proportion of cats with protective serum antiviral antibody titers increased (FPV [90%], FHV [56%], FCV [93%], and RV [98%]). With the exception of the FHV vaccine, there were no differences in the proportions of cats protected with inactivated virus versus MLV vaccines.

Conclusions and Clinical Relevance—Results suggest that exposure to FPV, FHV, and FCV is common among feral cats and that a high proportion of cats are susceptible to RV infection. Feral cats appeared to have an excellent immune response following vaccination at the time of neutering. Incorporation of vaccination into trap-neuter-return programs is likely to protect the health of individual cats and possibly reduce the disease burden in the community.

Virus seroprevalence among cats in North America

Levy, J.K.,  H. M, Scott, J. L. Lachtara , P. C. Crawford. (2006) Seroprevalence of feline leukemia virus and feline immunodeficiency virus infection among cats in North America and risk factors for seropositivity. Journal of the American Veterinary Medical Association 228 (3): 371-376

Objective—To determine seroprevalence of FeLV and FIV infection among cats in North America and risk factors for seropositivity.

Design—Prospective cross-sectional survey.

Animals—18,038 cats tested at 345 veterinary clinics (n = 9,970) and 145 animal shelters (8,068) between August and November 2004.

Procedure—Cats were tested with a point-of-care ELISA for FeLV antigen and FIV antibody. A multivariable random effects logistic regression model was used to identify risk factors significantly associated with seropositivity while accounting for clinic-to-clinic (or shelter) variability.

Results—409 (2.3%) cats were seropositive for FeLV antigen, and 446 (2.5%) cats were seropositive for FIV antibody; 58 (0.3%) cats were seropositive for infection with both viruses. Multivariable analysis indicated that age, sex, health status, and cat lifestyle and source were significantly associated with risk of seropositivity, with adults more likely to be seropositive than juveniles (adjusted odds ratios [ORs], 2.5 and 2.05 for FeLV and FIV seropositivity, respectively), sexually intact adult males more likely to be seropositive than sexually intact adult females (adjusted ORs, 2.4 and 4.66), and outdoor cats that were sick at the time of testing more likely to be seropositive than healthy indoor cats (adjusted ORs, 8.89 and 11.3).

Conclusions and Clinical Relevance—Results suggest that certain characteristics, such as age, sex, health status, and lifestyle, are associated with risk of FeLV and FIV seropositivity among cats in North America. However, cats in all categories were found to be at risk for infection, and current guidelines to test all cats at the time of acquisition and again during illness should be followed.

Prevalence of pathogens in feral cats in Florida

Luria, B. J., Levy, J. K., Lappin, M. R., Breitschwerdt, E. B., Legendre, A. M., Hernandez, J. A., Gorman, S.P. & Lee, I. T. (2004). Prevalence of infectious diseases in feral cats in Northern Florida. Journal of Feline Medicine and Surgery, 6(5), 287-296.

Objectives of this study were to determine prevalence of infection in feral cats in Northern Florida with a select group of infectious organisms and to determine risk factors for infection. Blood samples or sera from 553 cats were tested with a panel of antibody, antigen or PCR assays. Male cats were at higher risk for FIV, Mycoplasma haemofelis, and M. haemominutum. Infection with either FeLV or FIV was associated with increased risk for coinfection with the other retrovirus, M. haemofelis, or M. haemominutum. Bartonella henselae had the highest prevalence and was the only organism that did not have any associated risk for coinfection with other organisms. Feral cats in this study had similar or lower prevalence rates of infections than those published for pet cats in the United States. Thus, feral cats assessed in this study appear to be of no greater risk to human beings or other cats than pet cats.

FIV and FeLV dynamics

Courchamp, F., C. Suppo, E. Fromont, & C. Bouloux. 1997. Dynamics of two feline retroviruses (FIV and FeLV) within one population of cats. Proceedings of the Royal Society, Biological Sciences, 264(1383): 785–794.
We present a deterministic model of the dynamics of two microparasites simultaneously infecting a single host population. Both microparasites are feline retroviruses, namely Feline Immunodeficiency Virus (FIV) and Feline Leukaemia Virus (FeLV). The host is the domestic cat Felis catus. The model has been tested with data generated by a long-term study of several natural cat populations. Stability analysis and simulations show that, once introduced in a population, FIV spreads and is maintained, while FeLV can either disappear or persist. Moreover, introduction of both viruses into the population induces an equilibrium state for individuals of each different pathological class. The viruses never induce the extinction of the population. Furthermore, whatever the outcome for the host population (persistence of FIV only, or of both viruses), the global population size at the equilibrium state is only slightly lower than it would have been in the absence of the infections (i.e. at the carrying capacity), indicating a low impact of the viruses on the population. Finally, the impact of the diseases examined simultaneously is higher than the sum of the impact of the two diseases examined separately. This seems to be due to a higher mortality rate when both viruses infect a single individual.

FeLV dynamics

Fromont, E., D. Pontier, M. Langlais, F. Courchamp, & M. Artois. 1997. Modelling the feline leukemia virus (FeLV) in natural populations of cats (Felis catus). Theoretical Population Biology 52: 60–70.

A compartmental model was built in order to study the circulation and impact of Feline Leukemia Virus (FeLV) in populations of domestic cats. The model was tested with data from a long-term study of several feline populations. The study of stability shows that FeLV is maintained in the population with a stable equilibrium and a slight reduction of population size. Estimation of the transmission rate allows us to make a comparison with the values previously estimated in the literature. We compare the impact of mass vaccination or removal programmes in controlling FeLV infection, and conclude that vaccination is more efficient

FeLV on Iberian lynx

Meli M.L., Cattori V., Martínez F., López G., Vargas A., Palomares F., López-Bao J.V., Hofmann-Lehmann R. & Lutz H. 2010. Feline Leukemia virus infection: A threat for the survival of the critically endangered Iberian lynx (Lynx pardinus): Veterinary Immunology and Immunopathology, 134: 61-67

The Iberian lynx (Lynx pardinus) is considered the most endangered felid species in the world. To date, less than 200 animals remain in the wild. Low numbers and genetic uniformity may contribute to render this species particularly susceptible to infectious diseases. Different pathogens have been identified in Iberian lynxes; including several feline bacterial and viral agents. Within a 6-month period starting in December 2006, 12 lynxes living in the northern part of the Doñana area were found to be infected with feline leukemia virus (FeLV). Eleven of these animals were antigenemic, and four of them died in the wild in less than 6 months since the first infected animal had been discovered. The remaining viremic lynxes were captured and allocated to a quarantine center to stop the spread of the infection. An additional three animals died shortly in the quarantine center due to acute anemic disease. Sequencing of the envelope surface unit gene revealed a common origin for the FeLV found in all lynxes. The sequences were closely related to FeLV-A/61E, originally isolated from cats in the USA. Our data demonstrate that, similarly to FeLV, the introduction of a new or particularly pathogenic infection brought into the small population of Iberian lynxes by other wild carnivores or feral cats and dogs roaming in the same habitats have severe consequences. It could result in epidemics that have the potential to eradicate the entire lynx population

Pathogens from domestic cat on Iberian lynx

Meli M., Cattori V., Martínez F., López G., Vargas A., Simón M.A., Zorrilla I., Muñoz A., Palomares F., López-Bao J.V., Pastor J., Tandon R., Willi B., Hofmann-Lehmann R. & Lutz H. 2009. Feline Leukemia Virus and Other Pathogens as Important Threats to the Survival of the Critically Endangered Iberian Lynx (Lynx pardinus). PLoS ONE, 4(3): e4744

Background

The Iberian lynx (Lynx pardinus) is considered the most endangered felid species in the world. In order to save this species, the Spanish authorities implemented a captive breeding program recruiting lynxes from the wild. In this context, a retrospective survey on prevalence of selected feline pathogens in free-ranging lynxes was initiated.

Methodology/ Principal Findings

We systematically analyzed the prevalence and importance of seven viral, one protozoan (Cytauxzoon felis), and several bacterial (e.g., hemotropic mycoplasma) infections in 77 of approximately 200 remaining free-ranging Iberian lynxes of the Doñana and Sierra Morena areas, in Southern Spain, between 2003 and 2007. With the exception of feline immunodeficiency virus (FIV), evidence of infection by all tested feline pathogens was found in Iberian lynxes. Fourteen lynxes were feline leukemia virus (FeLV) provirus-positive; eleven of these were antigenemic (FeLV p27 positive). All 14 animals tested negative for other viral infections. During a six-month period in 2007, six of the provirus-positive antigenemic lynxes died. Infection with FeLV but not with other infectious agents was associated with mortality (p<0.001). Sequencing of the FeLV surface glycoprotein gene revealed a common origin for ten of the eleven samples. The ten sequences were closely related to FeLV-A/61E, originally isolated from cats in the USA. Endogenous FeLV sequences were not detected.

Conclusions/Significance

It was concluded that the FeLV infection most likely originated from domestic cats invading the lynx's habitats. Data available regarding the time frame, co-infections, and outcome of FeLV-infections suggest that, in contrast to the domestic cat, the FeLV strain affecting the lynxes in 2007 is highly virulent to this species. Our data argue strongly for vaccination of lynxes and domestic cats in and around lynx's habitats in order to prevent further spread of the virus as well as reduction the domestic cat population if the lynx population is to be maintained.

First detection of FeLV on Iberian lynx

Luaces I, Doménech A, García-Montijano M, Collado VM, Sánchez C, Tejerizo JG, Glaka M, Fernández P & Gómez-Lucía E. 2008. Detection of Feline Leukemia virus in the endangered Iberian lynx (Lynx pardinus). Journal of Veterinary Diagnostic Investigation, 20: 381-385

Feline retroviruses are rarely reported in lynx species. Twenty-one Iberian lynx (Lynx pardinus) blood and tissue samples collected from Doñana National Park and Los Villares (Sierra Morena) in southern Spain during 1993–2003 were analyzed by polymerase chain reaction to amplify nucleic acids from feline retroviruses. Six samples were positive for Feline leukemia virus (FeLV), but no samples tested positive for Feline immunodeficiency virus. The BLAST analysis indicated that 5 of the 6 sequences were closely related to FeLV strain Rickard subgroup A, whereas 1 sequence was identical to FeLV. To the authors' knowledge, this is the first report of FeLV in the endangered Iberian lynx.

FeLV and Iberian lynx

López G, López-Parra M, Fernández L, Martínez-Granados C, Martínez F, Meli ML, Gil-Sánchez JM, Viqueira N, Díaz-Portero MA, Cadenas R, Lutz H, Vargas A & Simón MA. 2009. Management measure to control a feline leukemia virus outbreak in the endangered Iberian lynx. Animal Conservation, 12: 173-182

The feline leukemia virus (FeLV) is a retrovirus that affects domestic cats all over the world. Its pathogenic effects generally include anemia, immunosuppression or tumors. Dissemination over populations is linked to cat sociality, because the virus is transmitted by direct contact. Although the domestic cat is its common host, FeLV infection has also been described in some wild felids. In the Iberian lynx Lynx pardinus, some sporadic FeLV infection cases have been reported since 1994, but an outbreak with the involvement of several animals has never been described until now. During spring 2007, an FeLV outbreak hit the Doñana (SW Spain) population. The infection rapidly spread throughout the densest subpopulation throughout Doñana. Infected animals showed very acute anemic disease, most of them dying in o6 months. To avoid FeLV dissemination, a control program was carried out that included removal of viremic lynxes, vaccination of negative individuals and reduction of the feral cat population. The program was implemented both in Donana and in Sierra Morena populations. In Doñana, around 80% of the total lynx population and 90% of the outbreak focus subpopulation were evaluated. Seven out of the 12 infected individuals found died and two reverted to latency; the remaining viremic animals have been kept in captivity. The outbreak appears to have been successfully confined to the subpopulation where the virus appeared and no more cases have been found since August 2007. In the larger Sierra Morena population, 8% of the lynx population was surveyed. Thirtyfour uninfected Iberian lynxes were vaccinated at least once. The FeLV prevalence was found to be 27% in the Doñana population and 0% in the Sierra Morena population.

Virus to control island populations of cats

Courchamp F & Sugihara G (1999) Modeling the biological control of an alien predator to protect island species from extinction. Ecological Applications, 9 (1): 112-123.

Introduced feral cat (Felis catus) populations are an important threat to many island vertebrate populations and to bird species in particular. Elimination of feral cat populations is desirable in most of these ecosystems. Release of a parasite species in these mostly immune-naive populations is thought to be an efficient eradication measure. Such an approach is theoretically investigated here, using a mathematical model that describes the effects of introducing a virus into the cat population on population dynamics of both the cat and its prey. We studied the effects of two types of introduced feline viruses: Feline Immunodeficiency Virus and Feline Leukemia Virus, both of which are good candidates for eradicating a cat population. Results show that eradication is possible with Feline Leukemia Virus, if natural immunity is sufficiently low. Feline Immunodeficiency Virus cannot fully eradicate cat populations, but can be an effective agent for long-term control of cat populations on islands where total cat eradication is not possible (e.g., there is a high likelihood of continued introduction of cats) or not desirable (e.g., when rats are present). Culling, which by itself would require a very prolonged and logistically demanding effort to eliminate cat populations, may be more efficient when applied simultaneously with
virus introduction.