Epizootiology of endoparasitic infections in pet dogs and cats presented to a veterinary teaching hospital

Prevalences of, and risk factors associated with, protozoan and helminth parasite infections were determined for pet dogs and cats presented to the teaching hospital of the University of Pennsylvania School of Veterinary Medicine. Of 2294 canine fecal specimens, 34.8% were found to contain one or more kinds of parasite, consisting of: hookworms (14.4%); Trichuris vulpis (12.3%); Giardia (7.2%); ascarids (5.5%); coccidia (2.7%); cestodes (1.6%). The following risk factors were identified with infection in dogs: age less than 2 years; urban locality; male sex. Gonadectomy was associated with decreased parasite prevalences in both male and female dogs. Significant seasonal variations in prevalences of hookworm, ascarid and Giardia infections were found in dogs. Of 452 feline fecal specimens tested, 24.6% were positive for parasites, including: ascarids (16.4%); Giardia (3.5%); coccidia (2.9%); cestodes (2.4%); hookworm (1.1%). Host age of less than 2 years was a significant risk factor associated with parasitism in cats. Of 1571 dogs tested for Dirofilaria immitis microfilaremia, 3.7% were positive. Non-urban locality was a significant risk factor for D. immitis infection in dogs.     

Prevalence and risk factors for Giardia and coccidia species of pet cats in 2003-2004

Prevalence and risk factors for feline coccidia and Giardia species infections were estimated for cats visiting 434 Banfield hospitals in 40 states in 2003-2004. Evaluated were 631,021 cats making 1,456,712 office visits (encounters) and having 211,105 fecal examinations. The overall fecal prevalences of coccidia and Giardia species were 1.4% and 0.58%, respectively. Cats at increased risk of coccidia infection were under 4 years of age, intact, and seen during the summer, fall, and spring months compared to winter. Cats at increased risk of Giardia species infection were under 4 years of age. Those at decreased risk were mixed breed and seen during the summer, fall, and spring. The highest regional risk of coccidia and Giardia species infection was for cats in the East South Central region and Mountain region, respectively, compared to the South Pacific region.     

Seroprevalences of antibodies against Bartonella henselae and Toxoplasma gondii and fecal shedding of Cryptosporidium spp, Giardia spp, and Toxocara cati in feral and pet domestic cats

OBJECTIVE: To compare seroprevalences of antibodies against Bartonella henselae and Toxoplasma gondii and fecal shedding of Cryptosporidium spp, Giardia spp, and Toxocara cati in feral and pet domestic cats. DESIGN: Prospective cross-sectional serologic and coprologic survey. ANIMALS: 100 feral cats and 76 pet domestic cats from Randolph County, NC. PROCEDURE: Blood and fecal samples were collected and tested. RESULTS: Percentages of feral cats seropositive for antibodies against B. henselae and T. gondii (93% and 63%, respectively) were significantly higher than percentages of pet cats (75% and 34%). Percentages of feral and pet cats with Cryptosporidium spp (7% of feral cats; 6% of pet cats), Giardia spp (6% of feral cats; 5% of pet cats), and T. cati ova (21% of feral cats; 18% of pet cats) in their feces were not significantly different between populations. Results of CBCs and serum biochemical analyses were not significantly different between feral and pet cats, except that feral cats had a significantly lower median PCV and significantly higher median neutrophil count. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that feral and pet cats had similar baseline health status, as reflected by results of hematologic and serum biochemical testing and similar prevalences of infection with Cryptosporidium spp, Giardia spp, and T. cati. Feral cats did have higher seroprevalences of antibodies against B. henselae and T. gondii than did pet cats, but this likely was related to greater exposure to vectors of these organisms.     

The veterinary and public health significance of hookworm in dogs and cats in Australia and the status of A. ceylanicum

There is no current information regarding the prevalence of hookworm in Australian dogs and cats and based on the results of studies conducted over 20 years ago, where high prevalences of helminths were recorded, the prophylactic administration of broad spectrum anthelmintics has been advocated. During this study, faecal samples were collected from dogs (n=1391) and cats (n=1027) across Australia. Samples were examined by microscopy and information regarding the demographics of each animal, and the management practices they experienced were recorded. A highly sensitive and species-specific PCR-RFLP technique was utilized to differentiate the various hookworm species which can infect dogs and cats directly from eggs in faeces. The prevalence of hookworm in dogs and cats was found to be 6.9% and 1.4%, respectively. Ancylostoma ceylanicum was detected for the first time in Australia in 10.9% of the dogs found positive for hookworm. Significantly, A. ceylanicum is capable of causing a patent infection in humans. After adjusting for other factors with multiple logistic regression, dogs from refuges, dogs originating from a tropical climatic zone, dogs aged 1 year or less, and those dogs which had not received anthelmintics were significantly more likely to be parasitized. Only univariate analysis was conducted for the cats as there were too few samples positive for hookworm. Cats were more likely to be infected with hookworm if they were from refuges, originated from a tropical climatic zone, and had not received treatment with anthelmintics. The results of this study demonstrates the importance of having current information regarding the prevalence of parasites of dogs and cats and the risk factors associated with infection, as well as the need to reassess the veterinary and public health concerns regarding hookworm infection and its control, which are currently based on out-dated information.     

Thermotolerant Campylobacters in domestic animals in a defined population in Buenos Aires,Argentina

We assessed the prevalence of Campylobacter jejuni in animals in a region of unsatisfied basic needs in the city of Buenos Aires and studied a few risk factors. First we conducted a census to identify all dwellings having pet animals (dogs, cats, and birds). Fecal samples were then taken for isolation and identification of strains. We observed 17% prevalence for dogs (95% CI: 13, 22), 16% for cats (95% CI: 8, 27) and 19% for birds (95% CI: 5, 42). In dogs, the highest prevalences were found in summer and in animals <1 year old; in cats, in autumn and those aged 3-5 years. Strains were identified as C. jejuni biotype II in 70% of isolates. In the population described here, dogs, cats and birds kept in households were potential sources of human Campylobacter infections.     

Prevalence of Feline Chlamydia psittaci and Feline Herpesvirus 1 in Cats with Upper Respiratory Tract Disease

The epidemiology of feline chlamydiosis and feline herpesvirus 1 (FHV1) infection in cats was determined using a duplex polymerase chain reaction assay. In cats with upper respiratory tract disease (URTD), prevalences of 66 (14.3%) of 462 cats and 98 (21.2%) of 462 cats were found for Chlamydia psittaci and FHV1, respectively. In cats without URTD, prevalences were 1/87 (1.1%) for both pathogens. Younger cats, cats sampled in summer, and cats with conjunctivitis were more likely to be positive for C psittaci than were cats sampled in other seasons and cats without conjunctivitis. Cats with recent contact with cats outside the household, cats with acute disease, and sneezing cats were more likely to be positive for FHV1 than were cats that had not had recent contact with cats outside the household, cats with chronic disease, and cats that were not sneezing. Purebred cats were less likely to be positive for FHV1 than were mixed breed cats and prevalence varied with year of sampling. Coinfection with both pathogens was lower than would be expected from their respective prevalences. Vaccinated cats were equally likely to be positive for FHV1 as unvaccinated cats. In sneezing cats FHV1 was more likely to be detected than C psittaci, particularly in acute cases, and when sneezing was not accompanied by conjunctivitis. Cats with reproductive disease concurrent with URTD were more likely to be infected with FHV1 than with C psittaci. Thus, the factors that should be considered in clinical diagnoses of C psittaci infections are the presence of conjunctivitis, age, and season, whereas contact with other cats, acute disease, and sneezing should be considered in diagnoses of FHV1 infection.     

Prevalence of infectious diseases in feral cats in Northern Florida

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.     

Seroprevalence of feline leukemia virus and feline immunodeficiency virus infection among cats in North America and risk factors for seropositivity

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.     

Association between patient-related factors and risk of calcium oxalate and magnesium ammonium phosphate urolithiasis in cats

OBJECTIVE: To determine whether breed, age, sex, or reproductive status (i.e., neutered versus sexually intact) was associated with the apparent increase in prevalence of calcium oxalate (CaOx) uroliths and the decrease in prevalence of magnesium ammonium phosphate (MAP) uroliths in cats over time. DESIGN: Case-control study. ANIMALS: Case cats consisted of cats with CaOx (n = 7,895) or MAP (7,334) uroliths evaluated at the Minnesota Urolith Center between 1981 and 1997. Control cats consisted of cats without urinary tract disease admitted to veterinary teaching hospitals in the United States and Canada during the same period (150,482). PROCEDURE: Univariate and multivariate logistic regression were performed. RESULTS: British Shorthair, Exotic Shorthair, Foreign Shorthair, Havana Brown, Himalayan, Persian, Ragdoll, and Scottish Fold cats had an increased risk of developing CaOx uroliths, as did male cats and neutered cats. Chartreux, domestic shorthair, Foreign Shorthair, Himalayan, Oriental Shorthair, and Ragdoll cats had an increased risk of developing MAP uroliths, as did female cats and neutered cats. Cats with CaOx uroliths were significantly older than cats with MAP uroliths. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that changes in breed, age, sex, or reproductive status did not contribute to the apparent reciprocal relationship between prevalences of CaOx and MAP uroliths in cats during a 17-year period. However, cats of particular breeds, ages, sex, and reproductive status had an increased risk of developing CaOx and MAP uroliths.     

Prevalence of feline infectious peritonitis in specific cat breeds

Although known that purebreed cats are more likely to develop feline infectious peritonitis (FIP), previous studies have not examined the prevalence of disease in individual breeds. All cats diagnosed with FIP at a veterinary teaching hospital over a 16-year period were identified. Breed, sex and reproductive status of affected cats were compared to the general cat population and to mixed breed cats evaluated during the same period. As with previous studies sexually intact cats and purebreed cats were significantly more likely to be diagnosed with FIP; males and young cats also had a higher prevalence of disease. Abyssinians, Bengals, Birmans, Himalayans, Ragdolls and Rexes had a significantly higher risk, whereas Burmese, Exotic Shorthairs, Manxes, Persians, Russian Blues and Siamese cats were not at increased risk for development of FIP. Although additional factors doubtlessly influence the relative prevalence of FIP, this study provides additional guidance when prioritizing differentials in ill purebreed cats.     

Epidemiologic features of Campylobacter infection among cats in the upper midwestern United States

OBJECTIVE: To describe the epidemiologic features of Campylobacter infection among cats in the Minneapolis-Saint Paul metropolitan area. DESIGN: Prevalence survey. ANIMALS: 152 cats examined at 3 private veterinary clinics and an animal humane society. PROCEDURES: Fecal samples were submitted for bacterial culture for Campylobacter spp. To determine the duration of Campylobacter carriage, follow-up fecal samples were collected from cats with positive Campylobacter culture results. RESULTS: Campylobacter organisms were cultured from 37 of the 152 (24%) fecal samples. Campylobacter isolates were identified as Campylobacter upsaliensis (29 cats), Campylobacter jejuni (2), and Campylobacter coli (1); species of the remaining 5 isolates could not be determined. Campylobacter organisms were isolated from 36 of the 122 (30%) cats that were < or = 1 year old but from only 1 of the 30 (3%) cats that were > 1 year old, and shedding was more common during the summer and fall months. No association between Campylobacter shedding and clinical signs of disease was identified. For 4 of 13 cats from which follow-up fecal samples were obtained, duration of Campylobacter carriage could not be determined because Campylobacter organisms were isolated from all follow-up samples. For the remaining 9 cats, median duration of Campylobacter carriage was 44 days. CONCLUSIONS AND CLINICAL RELEVANCE: C. upsaliensis can commonly be isolated from the feces of overtly healthy kittens in the Midwest United States. Because carriage may be prolonged, veterinarians should encourage good hand hygiene among owners of cats, especially among owners with new kittens in their household.     

Prevalence of feline immunodeficiency virus infection in domesticated and feral cats in eastern Australia

Serum samples from 340 pet cats presented to three inner city clinics in Sydney Australia, 68 feral cats from two separate colonies in Sydney, and 329 cattery-confined pedigree and domestic cats in eastern Australia, were collected over a 2-year period and tested for antibodies directed against feline immunodeficiency virus (FIV) using immunomigration (Agen FIV Rapid Immunomigration test) and enzyme-linked immunosorbent assay methods (Snap Combo feline leukaemia virus antigen/FIV antibody test kit, IDEXX Laboratories). Western blot analysis was performed on samples in which there was discrepancy between the results. Information regarding breed, age, gender, housing arrangement and health status were recorded for all pet and cattery-confined cats, while the estimated age and current physical condition were recorded for feral cats. The FIV prevalence in the two feral cat populations was 21% and 25%. The majority of FIV-positive cats were male (60-80%). The FIV prevalence in cattery-confined cats was nil. The prevalence of FIV in the pet cat sample population was 8% (27/340) with almost equal prevalence in 'healthy' (13/170) and 'systemically unwell' (14/170) cats. The age of FIV-positive pet cats ranged from 3 to 19 years; all FIV-positive cats were domestic shorthairs with outside access. The median age of FIV-positive pet cats (11 years) was significantly greater than the median age of FIV-negative pet cats (7.5 years: P<0.05). The prevalence of FIV infection in male pet cats (21/172; 12%) was three times that in female pet cats (6/168; 4%; P<0.05). With over 80% of this pet cat population given outside access and continued FIV infection present in the feral population, this study highlights the need to develop rapid, accurate and cost-effective diagnostic methods that are not subject to false positives created by concurrent vaccination against FIV. This is especially important in re-homing stray cats within animal shelters and monitoring the efficacy of the new vaccine, which has not been challenged against Australian strains. The absence of FIV within cattery-confined cats highlights the value in routine screening and indoor lifestyles. This study provides cogent baseline FIV prevalences in three cat subpopulations which can be used for appraising potential disease associations with FIV in Australia.     

Prevalence of naturally occurring Dirofilaria immitis infection among nondomestic cats housed in an area in which heartworms are endemic

OBJECTIVE: To determine prevalences of heartworm exposure (ie, positive heartworm antibody test results) and heartworm infection (ie, positive heartworm antigen test results or identification of mature heartworms at necropsy) among nondomestic cats housed in an area in rural North Carolina where Dirofilaria immitis is known to be endemic and among nondomestic cats housed in areas with a low prevalence of dirofilariasis or in an area considered to be free from heartworms. DESIGN: Cross-sectional prevalence survey. ANIMALS: 97 nondomestic cats in North Carolina (study population) and 29 nondomestic cats in Colorado; Queensland, Australia; or Auckland, New Zealand (control population). PROCEDURE: Results of serologic tests and postmortem examinations were reviewed. RESULTS: Results of heartworm antibody tests were positive for 57 of 75 (76%) study cats and 1 of 29 (3%) control cats. Male study cats had a significantly higher risk of heartworm exposure than did female study cats (relative risk, 1.3). Results of heartworm antigen tests were negative for all 47 study cats and 16 control cats that were tested. Postmortem examinations were performed on 21 study cats, and 1 (5%) was found to be infected with heartworms. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that nondomestic cats housed outdoors in the southeastern United States are at risk for heartworm exposure and infection, with male cats having a greater risk of exposure than female cats.     

Prevalence of Dirofilaria immitis and gastrointestinal helminths in cats euthanized at animal control agencies in northwest Georgia

Cats euthanized at six northwest Georgia animal control agencies were examined for adult Dirofilaria immitis in heart and lung tissue and presence of gastrointestinal helminth ova by fecal flotation. D. immitis were found in 4 of 184 cats (2.1%). The prevalence of feline dirofilariasis in northwest Georgia was lower than that found in other studies conducted in the southeastern United States, but closer to the prevalences occurring in areas of similar topography. Heartworm antigen and antibody tests performed on batched serum samples resulted in low sensitivity and high specificity. Gastrointestinal helminth ova were found in 39.6% of the fecal samples examined and 6.1% of the samples contained two or more species.     

Serological evidence of Ehrlichia spp. exposure in cats from northeastern Spain

There is little information about Ehrlichia canis as an infectious agent in cats. In order to estimate the prevalence of antibodies to E. canis in the feline population, 235 cat sera were analysed by indirect fluorescent-antibody test. With the objective to determine some risk factors associated with seropositivity, serum samples were divided into two groups: urban stray cats and pet cats. The seroprevalence detected was 17.9%. Most positive sera (83.3%) showed low antibody titres (<1:80). Seropositivity was very similar when comparing the two groups of animals: 17.4% in urban stray cats and 18.4% in pet cats. Results revealed that cats are exposed to Ehrlichia spp. infection, as the low antibody titres detected and the serological cross-reactivity between Ehrlichia species do not allow us to confirm E. canis exposure.     

Prevalences of various hemoplasma species among cats in the United States with possible hemoplasmosis

OBJECTIVE: To determine prevalences of various hemoplasma species among cats in the United States with possible hemoplasmosis and identify risk factors for and clinicopathologic abnormalities associated with infection with each species. DESIGN: Cross-sectional study. Animals-310 cats with cytologic evidence of hemoplasmosis (n = 9) or acute or regenerative anemia (309). PROCEDURES: Blood samples were tested by means of a broad-spectrum conventional PCR assay for hemoplasma DNA and by means of 3 separate species-specific real-time PCR assays for DNA from "Candidatus Mycoplasma haemominutum" (Mhm), Mycoplasma haemofelis (Mhf), and "Candidatus Mycoplasma turicensis" (Mtc). RESULTS: Overall prevalences of Mhm, Mhf, and Mtc infection were 23.2% (72/310), 4.8% (15/310), and 6.5% (20/310), respectively. Mixed infections were detected in 20 (6.5%) cats. Cats infected with hemoplasmas were more likely to be male than were uninfected cats. Infection with FeLV or FIV was significantly associated with infection with Mhf. Compared with uninfected cats, cats infected with Mhf had higher reticulocyte counts, nucleated RBC counts, and mean corpuscular volume; cats infected with Mhm had higher mean corpuscular volume; and cats infected with Mtc had higher monocyte counts. CONCLUSIONS AND CLINICAL RELEVANCE: Results supported the suggestion that these 3 hemoplasma species commonly occur among cats in the United States and that pathogenicity of the 3 species varies.     

National study of the gastrointestinal parasites of dogs and cats in Australia

The prevalence of gastrointestinal parasites in Australian pet dogs and cats was largely unknown prior to this study. Current recommendations for the prophylactic treatment of parasites in Australia are based on studies conducted 20-30 years ago. A total of 1400 canine and 1063 feline faecal samples were collected from veterinary clinics and refuges from across Australia. The overall prevalence of gastrointestinal parasites in dogs and cats was 23.9% (CI 21.7-26.1) and 18.4% (CI 16.1-20.7), respectively. Overall Giardia was the most prevalent parasite in dogs (9.3% CI 7.8-10.8) followed by hookworm (6.7% CI 5.4-8.0). Isospora felis was the most prevalent parasite in cats (5.6% CI 4.2-7.0), followed by Toxocara cati (3.2% CI 2.1-4.3). In conclusion the prevalence of intestinal helminths in Australian pet dogs and cats is low. Consequently, consideration should be given to the future use of anthelmintics and continued emphasis on pet owner education as means of preventing infection.     

Efficacy and safety of selamectin against gastrointestinal nematodes in cats presented as veterinary patients

A series of randomized, controlled, masked, field (veterinary patient) studies were conducted in the USA and Europe to evaluate the efficacy of selamectin, a novel macrocyclic lactone of the avermectin subclass, in the treatment of naturally acquired gastrointestinal nematode infections in cats. After confirmation of ascarid and/or hookworm infection, 298 cats of various ages and breeds were randomly assigned to treatment with selamectin (n=202) or an existing commercially approved positive-control product (n=96). Unit doses of selamectin (providing a minimum dosage of 6mgkg(-1)) were administered topically to the skin in a single spot at monthly intervals. Quantitative fecal examinations were performed on days 0 (before treatment), 30, and 60. In the selamectin-treated cats, fecal ascarid egg counts were reduced by 99.6 to 100% on day 30, and by 99.9 to 100% on day 60. Fecal hookworm egg counts were reduced by 98.3% on day 30, and by 100% on day 60 in the selamectin-treated cats. The positive-control products achieved reductions in egg counts of 96.5 to 100% (ascarids) and 98.9 to 99.9% (hookworms). These studies have shown that monthly topical administration of selamectin is safe and highly effective in the treatment of naturally acquired ascarid and hookworm infections in cats.     

Uterine neoplasia in 13 cats.

Thirteen uterine tumors were diagnosed in 13 cats and accounted for 0.29% of all feline neoplasms received during a 9.6-year period. Age at diagnosis ranged from 3 to 16 years; median 9 years. Six were Domestic Shorthair cats, and 7 were purebred cats of 5 different breeds. Eight adenocarcinomas and 1 mixed Müllerian tumor (adenosarcoma) comprised the endometrial tumors. Myometrial tumors included 3 leiomyomas and 1 leiomyosarcoma. One of the adenocarcinomas developed in the uterine stump of an ovariohysterectomized cat; the other cats were sexually intact. Concurrent mammary adenocarcinoma was diagnosed in 1 cat with uterine adenocarcinoma and in another with uterine leiomyoma. Tumors were discovered during elective ovariohysterectomy in 2 cats, but at least 3 others had experienced reproductive problems (infertility or pyometra). Five cats presented for abdominal or pelvic masses. Endometrial adenocarcinomas were positive immunohistochemically for cytokeratins and negative for smooth muscle actin (SMA): 1 of 6 cats was positive for vimentin and 4 of 8 were positive for estrogen receptor-alpha (ER alpha). Adenosarcoma stromal cells were positive for vimentin and ER alpha but negative for cytokeratins and SMA. Smooth muscle tumors were positive for vimentin and SMA and negative for cytokeratins. Leiomyomas, but not the leiomyosarcomas, were positive for ER alpha. Adenocarcinomas in 4 cats had metastasized by the time of ovariohysterectomy. Two other cats were euthanized 5 months after ovariohysterectomy; at least one of these cats had developed an abdominal mass that was not examined histologically. Only 2 cats with endometrial adenocarcinoma had disease-free intervals longer than 5 months after surgery. Metastasis was not detected in any mesenchymal tumor; however, these cats were either euthanized on discovery of the tumor or the tumor was first detected at necropsy.     

Nonlinear mixed models of growth curves from domestic shorthair cats in a breeding colony,housed in a seasonal facility to predict obesity

Obesity is highly prevalent in pet cats (Felis silvestris catus) and is associated with several comorbidities, yet very little is understood about the early life risk factors. The aim of this study was to develop a mathematical model that describes growth in cats, to determine which early life variables were associated with being overweight in adulthood and to identify when during life the overweight phenotype developed in a colony of cats. We used pedigree, birth and growth data of 212 colony cats that were fed ad libitum from weaning. A nonlinear mixed‐effects model was fitted to the body weight data to describe growth curves. A subset of 146 cats that had reached 9 years of age was used to evaluate the body weight curves to 9 years, and candidate early life predictors of peak weight were evaluated using logistic regression. In contrast with other species, candidates such as maternal factors, birth weight and litter size were not significant risk factors for adult obesity. Male sex, body weight around 15 weeks of age and being born during the increasing photoperiod were significantly associated with being overweight at 9 years. The growth equation created can be used to predict peak body weight, when sex and season of birth are included. Thus, the trajectory to obesity is determined early in life in cats, and early intervention appears essential to prevent obesity in pet cats.