A review of feral cat control

Animal overpopulation including feral cats is an important global problem. There are many stakeholders involved in the feral cat debate over 'what to do about the problem', including those who consider them a nuisance, the public at risk from zoonotic disease, people who are concerned about the welfare of feral cats, those concerned with wildlife impacts, and the cats themselves. How best to control this population is controversial and has ranged from culling, relocation, and more recently 'trap neuter return' (TNR) methods. Data support the success of TNR in reducing cat populations, but to have a large impact it will have to be adopted on a far greater scale than it is currently practised. Non-surgical contraception is a realistic future goal. Because the feral cat problem was created by humans, concerted educational efforts on responsible pet ownership and the intrinsic value of animals is an integral part of a solution.     

Fertility control as a management tool for feral horse populations

This report addresses the basic reproductive biology of the North American feralhorse. With a basis of population records to establish a framework, experimental studies on specific and seasonal aspects of sexual behavior and social behavior are discussed with special attention to elimination marking (scent marking) behavior in stallions and estrus behavior in mares. In addition, the physiological basis for the hormonal control of reproduction in male and female feralhorses is presented, with discussion of specific experiments. Definite and correlated seasonal patterns of plasma testosterone and elimination marking behavior in stallions are examined, and hormonal patterns and events of the estrus cycle of the mare are presented. These aspects of feral horsereproduction are then interpreted with attention to integration of processes, and comparisons between the feral and domestic horse are made.     

A mobility model for classical swine fever in feral pig populations

We present a simulation model which explicitly captures the movement of wild animals over the landscape and the effect which herd mobility has on the temporal and spatial course of an epidemic. Using the example of classical swine fever in feral pig populations in the tropical savannas, we demonstrate that seasonal factors influencing population density and movement patterns are an important factor in the transmission of the disease. Pig population density is much greater at the start of the dry season than at the start of the wet season, with an epidemic most likely to occur if initiated at the start of the dry season. Spatial heterogeneity due to scarcity of water in the dry season causes herds to congregate around water sources. This concentration of herds, and the consequential isolation of sub-populations, reduces overall disease transmission compared with a model where the population is more evenly distributed over the landscape. The presence of adult male pig herds, which travel over greater distances than family herds, is shown to increase the overall scale of an outbreak in the dry season by connecting together otherwise isolated family herds. Eradication strategies are more likely to be successful in the dry season if they target long-range adult male herds. Our simulation method is generic and is equally applicable to other diseases where the host species is mobile.     

Helminth parasitisms among intermingling insular populations of white-tailed deer, feral cattle, and feral swine.

Helminth infections among free-ranging, intermingling populations of white-tailed deer (Odocoileus virginianus), cattle (Bos taurus), and swine (Sus scrofa) on an island off the Georgia coast were studied. Of 39 species of helminths collected, 19 were found in deer, 17 in cattle, and 13 in swine. Of 28 species of helminths recovered from ruminants, 8, viz, Capillaria bovis, Cooperia punctata, Dictyocaulus viviparus, Gongylonema pulchrum, G verrucosum, Haemonchus contortus, Moniezia benedeni, and Trichostrongylus axei, occurred in both deer and cattle. Common liver flukes (Fasciola hepatica) infected cattle and swine but not deer. Only 1 helminth, G pulchrum, infected deer, cattle, and swine. The findings suggested that helminths harbored by the host species are distinct, with little exchange occurring.     

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.     

Infectious disease prevalence in a feral cat population on Prince Edward Island, Canada

Ninety-six feral cats from Prince Edward Island were used to determine the prevalence of selected infectious agents. The prevalence rates were 5.2% for feline immunodeficiency virus, 3.1% for feline leukemia virus, 3.1% for Mycoplasma haemofelis, 8.4% for Candidatus Mycoplasma haemominutum, 2.1% for Bartonella spp. and 29.8% for exposure to Toxoplasma gondii. Oocysts of T. gondii were detected in 1.3% of the fecal samples that were collected. Gender and retroviral status of the cats were significantly correlated with hemoplasma infections. Use of a flea comb showed that 9.6% of the cats had fleas; however, flea infestation was not associated with any of the infectious agents.     

Broad-scale possum and ferret correlates of macroscopic Mycobacterium bovis infection in feral ferret populations

AIMS: To examine the relationships between the prevalence of macroscopic Mycobacterium bovis infection (bovine tuberculosis) in feral ferrets (Mustela furo), the abundance of ferrets, and the abundance of brushtail possums (Trichosurus vulpecula) . METHODS: Data on the prevalence of macroscopic M. bovis infection in ferrets, abundance of ferrets, and abundance of possums were analysed from 12 comparable independent broad-scale surveys. RESULTS: The prevalence of macroscopic M. bovis infection in ferrets was positively correlated with possum abundance but unrelated to ferret abundance, suggesting that possums are an important source of M. bovis infection in ferrets. The lack of any positive relationship between the prevalence of M. bovis infection in ferrets and ferret abundance does not support the hypothesis that per capita transmission rates, and therefore disease prevalence, should be higher at higher ferret abundance. CONCLUSION: The results support the hypothesis that tuberculous possums are the major underlying source of M. bovis infection for feral ferrets in New Zealand.     

Spirometra erinacei / S. erinaceieuropaei in a feral cat in Manawatu with chronic intermittent diarrhoea

CASE HISTORY: A feral cat captured in the Manawatu region of New Zealand was treated for worms and fleas, and kept confined in a metabolic cage. It showed good appetite and weight gain but had intermittent watery, yellow diarrhoea.

CLINICAL FINDINGS: Clinical examination under sedation was unremarkable and routine blood tests showed no significant abnormalities. The cat was negative for feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). Different canned cat foods did not alter the course of the diarrhoea, and the cat was euthanised 6 months after capture. At necropsy, two sections of adult Spirometra tapeworms were found in the jejunum and typical Spirometra eggs were found in colonic contents. Molecular identification of the parasite was undertaken, using the cytochrome- c oxidase subunit-1 gene (cox1) sequence.

DIAGNOSIS: Chronic intermittent diarrhoea associated with Spirometra erinacei / S. erinaceieuropaei infection.

CLINICAL RELEVANCE: Spirometra has not been reported in New Zealand before but has been associated with gastrointestinal disease in cats in other parts of the world. It requires speciestargeted treatment to be eliminated effectively, and is zoonotic. Diagnosis could be diffi cult for clinicians who are not familiar with the parasite and its life cycle.     

Spirometra erinacei / S. erinaceieuropaei in a feral cat in Manawatu with chronic intermittent diarrhoea

CASE HISTORY: A feral cat captured in the Manawatu region of New Zealand was treated for worms and fleas, and kept confined in a metabolic cage. It showed good appetite and weight gain but had intermittent watery, yellow diarrhoea. CLINICAL FINDINGS: Clinical examination under sedation was unremarkable and routine blood tests showed no significant abnormalities. The cat was negative for feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). Different canned cat foods did not alter the course of the diarrhoea, and the cat was euthanised 6 months after capture. At necropsy, two sections of adult Spirometra tapeworms were found in the jejunum and typical Spirometra eggs were found in colonic contents. Molecular identification of the parasite was undertaken, using the cytochrome-c oxidase subunit-1 gene (cox1) sequence. DIAGNOSIS: Chronic intermittent diarrhoea associated with Spirometra erinacei / S. erinaceieuropaei infection. CLINICAL RELEVANCE: Spirometra has not been reported in New Zealand before but has been associated with gastrointestinal disease in cats in other parts of the world. It requires species targeted treatment to be eliminated effectively, and is zoonotic. Diagnosis could be difficult for clinicians who are not familiar with the parasite and its life cycle.     

Preferential sexual transmission of pseudorabies virus in feral swine populations may not account for observed seroprevalence in the USA

This paper compares the behavior of two competing models for the transmission of pseudorabies virus in feral swine in the USA. In first model, horizontal (non-sexual) density dependent transmission is the only transmission modality. In the second model, the only transmission modality is sexual transmission between mature males and females. The comparison of model behavior was carried out to test the hypothesis that preferential sexual transmission of PRV in feral swine can account for the seroprevalence observed in the field. The observed range of seroprevalence of PRV in mature feral swine in the USA is consistent with a preferential sexual transmission only if the feral swine mating system is a random mating system or a polygynous system in which there is a relatively large rate of acquisition of new mates. The observed range of seroprevalence of PRV in mature feral swine in the USA is not consistent with a preferential sexual transmission if there is mate guarding. This is important because the National Pseudorabies Surveillance Plan deems monitoring the risk of PRV introduction from feral swine to be a "minor objective" both in terms of the scope of the plan and with respect to the resources allocated. The rationale for this statement was derived from experimental studies, which suggested that the PRV indigenous to feral swine in the USA is preferentially sexually transmitted.