Toxoplasmosis in Cats: Zoonotic Risks and Management

Etiology and Life Cycle

Toxoplasmosis is caused by the obligate intracellular apicomplexan parasite Toxoplasma gondii. Felids, including domestic cats, serve as the definitive host in which the parasite completes its sexual cycle and produces oocysts [1, 2]. The life cycle involves both sexual replication in the feline intestinal epithelium and asexual replication in a wide range of intermediate hosts, including mammals and birds [1]. After ingestion of tissue cysts containing bradyzoites, cats shed unsporulated oocysts in feces following a prepatent period of 3 to 10 days [2]. Sporulation occurs in the environment within 1 to 5 days, rendering oocysts infectious [3]. A single cat can shed millions of oocysts, and shedding typically lasts 1 to 3 weeks [2]. The parasite also undergoes asexual replication in intermediate hosts, forming tachyzoites during acute infection and bradyzoites within tissue cysts during chronic infection [1]. The sexual development of T. gondii in the feline intestinal tract has been characterized at the single-cell level, revealing distinct transcriptional programs for merozoite, gametocyte, and oocyst stages [2]. MicroRNA expression dynamics in the feline small intestine during infection further elucidate host-parasite interactions at the molecular level [4].

Epidemiology

Toxoplasma gondii infection is distributed globally, with seroprevalence varying widely by geographic region, cat population, and management practices [5, 6, 7]. Seroprevalence in privately-owned cats and community cats in Hong Kong was reported at 11.4% and 18.2%, respectively, with community cats showing higher exposure risk [5]. In Jordan, seroprevalence in cats reached 42.3% with molecular detection of T. gondii DNA in 18.3% of fecal samples [6]. Studies in urban informal settlements in Brazil demonstrated that environmental degradation and social marginalization are associated with increased T. gondii exposure in both companion animals and wildlife [8, 7]. Seroprevalence in dogs from the Pantanal region of Brazil was also high, reflecting widespread environmental contamination [9]. In Bangladesh, genotype distribution analysis in animals revealed predominance of Type I and Type II lineages, with risk factors including free-roaming behavior and access to raw meat [10]. Fecal shedding of T. gondii DNA was detected in 8.7% of stray cats in Bangkok, Thailand, confirming ongoing environmental contamination [3]. Seroprevalence in veterinary medicine professionals and students in Mexico was 15.6%, indicating occupational exposure risk [11]. The parasite has been detected in reproductive tissues of companion animals from neutering programs, suggesting potential vertical transmission pathways [12]. Seroprevalence in goats from Nigeria was 34.7%, with risk factors including age and management system [13]. In dairy cattle from Turkey, seroprevalence was 12.3% [14]. In pigs from eastern Spain, low seroprevalence (2.1%) was associated with intensive farming and controlled animal entry [15]. In deer from Iraq, seroprevalence was 9.8% [16]. In equine aborted fetuses in Brazil, molecular detection confirmed transplacental transmission [17]. In aborted goat fetuses in Algeria, histopathological and molecular detection confirmed T. gondii as a cause of abortion [18].

Clinical Signs in Cats

Most immunocompetent cats infected with T. gondii remain asymptomatic [6]. Clinical disease occurs more frequently in kittens, immunosuppressed cats, or those co-infected with other pathogens. The most common clinical manifestations include fever, lethargy, anorexia, and lymphadenopathy. Ocular toxoplasmosis presents as uveitis, chorioretinitis, and anterior chamber inflammation [19]. Neurological signs include ataxia, seizures, tremors, and behavioral changes, reflecting cerebral involvement [20]. Respiratory signs such as dyspnea and cough may occur with pulmonary toxoplasmosis. Hepatic and pancreatic involvement can cause icterus and vomiting. Myocarditis may lead to arrhythmias and congestive heart failure. The AB blood group system phenotype does not play a role in T. gondii infection susceptibility in cats [21]. Chronic infection is typically subclinical, with tissue cysts persisting in neural and muscular tissues.

Pathology

Gross pathological findings in acute feline toxoplasmosis include multifocal necrosis in the liver, lungs, spleen, and lymph nodes. Histopathological examination reveals necrotizing inflammation with intracellular and extracellular tachyzoites. In the central nervous system, glial nodules, perivascular cuffing, and microglial aggregates are observed. Ocular lesions include granulomatous chorioretinitis with lymphoplasmacytic infiltration. In the small intestine, sexual stages (meronts, gamonts, and oocysts) are found within enterocytes during the acute shedding phase [2]. Tissue cysts containing bradyzoites are found in skeletal muscle, cardiac muscle, and brain during chronic infection. In aborted fetuses, necrotizing placentitis and fetal encephalitis are characteristic [17, 18].

Diagnostics

Serological Methods

Serological detection of anti-T. gondii antibodies is the primary diagnostic approach in cats. Commercial ELISA kits detect IgM and IgG antibodies, with IgM indicating recent or active infection and IgG indicating chronic or past exposure [22, 23]. The modified agglutination test (MAT) is considered a reference standard for seroprevalence studies [5, 6]. A double-antigen sandwich colloidal gold immunochromatographic strip has been developed for rapid serological detection across multiple host species, including cats [22]. A SAG1-based colloidal gold immunochromatographic strip has been validated for swine and shows cross-species applicability [23]. MIC17A has been evaluated as both an entero-epithelial and chronic stage marker for detection of feline toxoplasmosis [24].

Molecular Methods

PCR-based assays detect T. gondii DNA in blood, tissues, aqueous humor, and feces. Conventional PCR targeting the B1 gene or 529 bp repeat element is widely used [3, 6]. An antisense PCR assay has been developed and evaluated for detection in domestic cats, demonstrating improved sensitivity compared to conventional PCR [25]. Real-time quantitative PCR (qPCR) allows quantification of parasite burden. PCR detection in fecal samples is challenging due to low oocyst shedding and PCR inhibitors, but remains useful for epidemiological studies [3]. Molecular detection in reproductive tissues has confirmed vertical transmission potential [12].

Fecal Examination

Microscopic examination of feces using flotation techniques can detect oocysts, but sensitivity is low due to intermittent shedding and morphological similarity to other coccidian oocysts. Bioassay in mice remains a gold standard for oocyst detection but is impractical for routine use.

Immunochromatographic Strips

Rapid immunochromatographic strips provide point-of-care serological diagnosis with results available in 10 to 15 minutes [22, 23]. These strips use recombinant antigens such as SAG1 or GRA proteins and have shown high sensitivity and specificity in field validation studies [22, 23].

Treatment

Treatment of clinical feline toxoplasmosis aims to reduce tachyzoite replication and control inflammation. The standard therapeutic regimen includes clindamycin administered orally or parenterally at 10 to 12 mg/kg every 12 hours for 2 to 4 weeks. Alternative antibiotics include trimethoprim-sulfonamide combinations, azithromycin, and pyrimethamine combined with sulfadiazine. Corticosteroids such as prednisolone are indicated for ocular toxoplasmosis to control immune-mediated inflammation. Supportive care includes fluid therapy, nutritional support, and anticonvulsants for neurological cases. Treatment does not eliminate tissue cysts, and recrudescence can occur during immunosuppression.

Control and Prevention

Environmental Management

Preventing environmental contamination with oocysts is the cornerstone of control. Litter boxes should be cleaned daily before oocysts sporulate and become infectious. Feces should be disposed of in sealed bags. Pregnant women and immunocompromised individuals should avoid handling cat litter or wear disposable gloves and wash hands thoroughly afterward [26]. The topic of cat toxoplasmosis baby risk is a frequent concern in veterinary practice; seronegative pregnant women should be advised to avoid contact with stray cats, raw meat, and gardening in soil potentially contaminated with cat feces [26].

Feeding Practices

Cats should be fed commercial cooked or canned food to prevent ingestion of tissue cysts. Raw meat diets, including raw beef, pork, lamb, or game meat, pose a significant risk for acquiring T. gondii infection [10]. Hunting of rodents and birds should be prevented by keeping cats indoors.

Vaccination

No commercial vaccine for feline toxoplasmosis is currently available. Gene-edited live-attenuated vaccines have shown promise in experimental models, with recent advances focusing on deletion of virulence genes to create safe and immunogenic strains [27]. mRNA vaccine strategies and One Health approaches are under investigation [28]. Antigen discovery efforts have identified multiple candidate antigens, including SAG1, MIC17A, and GRA proteins [28, 24].

Public Health Education

Veterinary professionals play a key role in educating cat owners about zoonotic risks. Knowledge and practices regarding toxoplasmosis among pregnant women and university students vary widely, indicating a need for targeted educational interventions [29, 30]. In Côte d'Ivoire, first report of knowledge and practices among pregnant women revealed significant gaps in awareness of transmission routes [29]. In Iraq, university students showed moderate knowledge levels [30]. In Brazil, ocular health assessment in Quilombola communities revealed associations between toxoplasmosis seropositivity and visual impairment [31]. In patients with sickle cell disease, seroprevalence was elevated and associated with blood transfusion history [32]. In renal transplant recipients, cerebral toxoplasmosis is a rare but severe complication [33]. In children, T. gondii seropositivity has been associated with psychotic experiences and reduced grey matter volume in population-based cohort studies [34]. In women with abortion or stillbirth history, seropositivity was significantly higher than in controls, confirming the role of T. gondii in reproductive failure [35].

Zoonotic Risk Management

The primary zoonotic risk from cats is ingestion of sporulated oocysts from contaminated environments. Secondary risks include ingestion of undercooked meat containing tissue cysts and congenital transmission from primary maternal infection during pregnancy [26]. The risk of cat toxoplasmosis baby transmission is highest when a pregnant woman acquires primary infection during gestation. Veterinary guidance should emphasize that indoor cats fed commercial diets pose minimal risk, while outdoor cats that hunt and consume raw meat are at higher risk of shedding oocysts [5, 6]. Immunocompromised individuals, including those with HIV/AIDS, organ transplant recipients, and patients on immunosuppressive therapy, should follow strict hygiene protocols when handling cats or cleaning litter boxes [33]. The parasite can alter host behavior in intermediate hosts, though the clinical significance of this phenomenon in cats remains under investigation [20].

flowchart TD
    A[Cat ingests tissue cysts from raw meat or prey], > B[Sexual replication in feline intestinal epithelium]
    B, > C[Oocyst shedding in feces]
    C, > D[Sporulation in environment 1-5 days]
    D, > E[Ingestion by intermediate hosts]
    E, > F[Asexual replication: tachyzoites acute]
    F, > G[Tissue cyst formation: bradyzoites chronic]
    G, > A
    D, > H[Direct ingestion by humans]
    H, > I[Human infection]
    I, > J[Congenital transmission if primary infection during pregnancy]
    I, > K[Ocular toxoplasmosis]
    I, > L[Cerebral toxoplasmosis in immunocompromised]

References

[1] Sena F, Hakimi M-A, Francia ME. Proliferating toward sex: characterization of cell division of Toxoplasma gondii's pre-sexual stages. mBio. 2026. https://pubmed.ncbi.nlm.nih.gov/42153709/

[2] Alrubaye HS, Reilly SM, da Silva R et al. A single-cell atlas of Toxoplasma sexual development in the feline intestinal tract. Nat Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/42020723/

[3] Kengradomkij C, Chimnoi W, Kamyingkird K et al. PCR detection of Toxoplasma gondii DNA in fecal samples from stray cats in Bangkok Metropolitan, Thailand. Food Waterborne Parasitol. 2026. https://pubmed.ncbi.nlm.nih.gov/42094705/

[4] Zhai B, Bao B, Xie SC et al. Dynamic landscape of microRNA expression in the feline small intestine during Toxoplasma gondii infection. Parasit Vectors. 2026. https://pubmed.ncbi.nlm.nih.gov/41965856/

[5] Elsohaby I, Zubair M, Baqar Z et al. Seroprevalence of Toxoplasma gondii and associated demographic factors in privately-owned dogs, cats, and community cats in Hong Kong. BMC Vet Res. 2026. https://pubmed.ncbi.nlm.nih.gov/42135800/

[6] Alkhatatbeh SK, Lafi SQ, Hammad HB et al. The first seroprevalence and molecular detection of toxoplasmosis infecting cats in Jordan with associated risk factors. Vet Parasitol Reg Stud Reports. 2026. https://pubmed.ncbi.nlm.nih.gov/41741047/

[7] Bazan L, Argibay HD, Borges-Silva W et al. Seroprevalence and risk factors for Toxoplasma gondii infection in wild, domestic and companion animals in urban informal settlements from Salvador, Brazil. PLoS Negl Trop Dis. 2025. https://pubmed.ncbi.nlm.nih.gov/41401226/ *** Disclaimer: This article is for educational and informational purposes only. It is not intended to substitute for professional veterinary advice, diagnosis, treatment, or regulatory guidance. Always consult a licensed veterinarian or qualified specialist regarding animal health, disease diagnosis, and therapeutic decisions.

[8] Eyre MT, Wang JY, Carneiro IO et al. Social marginalisation, environmental degradation and Toxoplasma gondii exposure in urban informal settlements in Brazil. PLoS Negl Trop Dis. 2026. https://pubmed.ncbi.nlm.nih.gov/42330015/

[9] Artiaga-Silva GL, de Lima Ruy Dias ÁF, Carvalho MR et al. High Seroprevalence Rates of Toxoplasma gondii and Neospora caninum in Dogs in the Pantanal Region of Mato Grosso, Brazil. Acta Parasitol. 2026. https://pubmed.ncbi.nlm.nih.gov/41843222/

[10] Biswas PK, Aryal D, Tarak AN et al. Genotype distribution and risk factors of Toxoplasma gondii infection in animals of Trishal, Bangladesh. PLoS One. 2026. https://pubmed.ncbi.nlm.nih.gov/41528989/

[11] de Velasco-Reyes I, Torres-García SE, Hernández-Rangel JJ et al. Seroprevalence of Toxoplasma gondii Infection in Veterinary Medicine Professionals and Students in Aguascalientes, Mexico. Epidemiologia (Basel). 2026. https://pubmed.ncbi.nlm.nih.gov/42201205/

[12] Murata FHA, Barboza JP, de Souza CAG et al. Investigation of Toxoplasma gondii in reproductive tissues of companion animals from a municipal neutering program. Vet Parasitol Reg Stud Reports. 2026. https://pubmed.ncbi.nlm.nih.gov/41651631/

[13] Muhammad AS, Kudi AC, Mohammed A et al. Public health significance of prevalence and risk factors associated with Toxoplasma gondii infection in goats sampled from two quarantine facilities and an institutional farm in Maiduguri metropolis, Borno state, Nigeria. Sci Rep. 2026. https://pubmed.ncbi.nlm.nih.gov/42020619/

[14] Hanedan B, Taş BZ, Yıldırım E et al. Investigation of Toxoplasma gondii seroprevalence and associated risk factors in dairy cattle in the Eastern Anatolia region of Türkiye. Vet Parasitol Reg Stud Reports. 2026. https://pubmed.ncbi.nlm.nih.gov/41819961/

[15] Marín-García PJ, Ballesteros-García O, Martínez-Sáez L et al. Low seroprevalence of Toxoplasma gondii in pig farms (Sus scrofa domesticus) of eastern Spain in intensive farms with control of animal entry. Vet Parasitol Reg Stud Reports. 2026. https://pubmed.ncbi.nlm.nih.gov/41741032/

[16] Aziz KJ, Mikaeelb FB, Nasrullah OJ et al. Seroepidemiological investigation of Toxoplasma gondi and Neospora caninum in local Deers in Erbil, Iraq. Vet Parasitol Reg Stud Reports. 2026. https://pubmed.ncbi.nlm.nih.gov/42034957/

[17] Pinto GOA, Silva RAD, Oliveira PRF et al. Molecular detection of Toxoplasma gondii in an aborted equine fetus and serological evidence of infection in mares enrolled in embryo transfer programs in Brazil. J Equine Vet Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42252005/

[18] Ait Issad N, Mohamed Cherif A, Mebkhout F et al. First report of molecular and histopathological detection of Toxoplasma gondii in aborted fetal goat myocardium in Algeria with associated risk factors. Parasitol Int. 2026. https://pubmed.ncbi.nlm.nih.gov/41864556/

[19] Askaryanzardak A, Kakkassery V, Tartaglione Gracia GP et al. [Ocular toxoplasmosis in adults : Refresher course]. Ophthalmologie. 2026. https://pubmed.ncbi.nlm.nih.gov/41603939/

[20] Loeb J. Thrill seekers: how parasites change host behaviour. Vet Rec. 2026. https://pubmed.ncbi.nlm.nih.gov/41481062/

[21] Spada E, Tattarletti G, Proverbio D et al. The AB Blood Group System Phenotype Does Not Play a Role in Toxoplasma gondii Infection in Cats. Pathogens. 2025. https://pubmed.ncbi.nlm.nih.gov/41471183/

[22] Mu X, Chen C, Pu X et al. Development and Field Validation of a Double-Antigen Sandwich Colloidal Gold Immunochromatographic Strip for Detection of Toxoplasma gondii Antibodies in Multiple Host Species. Transbound Emerg Dis. 2026. https://pubmed.ncbi.nlm.nih.gov/42253330/

[23] Chen XX, Sun H, Liang Y et al. Development of a SAG1-based colloidal gold immunochromatographic strip for rapid serological detection of swine Toxoplasma gondii. Parasit Vectors. 2026. https://pubmed.ncbi.nlm.nih.gov/42169035/

[24] Günay-Esiyok Ö, Koçkaya ES, Yılmaz R et al. The Potential of MIC17A both as an Entero-epithelial and Chronic Stage Marker for Detection of Feline Toxoplasmosis. Curr Microbiol. 2026. https://pubmed.ncbi.nlm.nih.gov/41874672/

[25] Li YY, Bai SY, Yu HQ et al. Development and evaluation of an antisense PCR assay for Toxoplasma gondii detection in domestic cats. Vet Parasitol. 2026. https://pubmed.ncbi.nlm.nih.gov/41724116/

[26] Gharbi M, Yera H, Dupouy-Camet J. [The cat, the women and the toxoplasma: What advice should be given to a pregnant woman who is seronegative for toxoplasmosis and owns a cat?]. Gynecol Obstet Fertil Senol. 2026. https://pubmed.ncbi.nlm.nih.gov/41628830/

[27] Sang X, Zhang H, Zhang Y et al. Gene-edited live-attenuated vaccines against Toxoplasma gondii: recent advances and future frontiers. Parasit Vectors. 2026. https://pubmed.ncbi.nlm.nih.gov/42252477/

[28] Qadeer A, Tharwat M, Khan MZ et al. Advances and Translational Challenges in Toxoplasma gondii Vaccine Development: From Antigen Discovery to mRNA and One Health Strategies. Vet Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/42188907/

[29] Henriette BA, Jémima EK, Jean-Sébastien MA et al. First report of knowledge and practices towards toxoplasmosis among pregnant women in primary care in Abidjan, Côte d'Ivoire. Trop Parasitol. 2026. https://pubmed.ncbi.nlm.nih.gov/42199683/

[30] Chalabi KN, Jabar Bakr E. Toxoplasmosis - knowledge among university students in Erbil, Iraq: a cross-sectional study. Int J Environ Health Res. 2026. https://pubmed.ncbi.nlm.nih.gov/41873025/

[31] Filho SCC, Moron SE, Ferreira RG et al. Risk Factors and Ocular Health Associated with Toxoplasmosis in Quilombola Communities. Microorganisms. 2026. https://pubmed.ncbi.nlm.nih.gov/41597614/

[32] Orish VN, Tetteh RE, Adzah D et al. Toxoplasma gondii seropositivity among patients with sickle cell disease: Prevalence and association with blood transfusion history. PLoS One. 2026. https://pubmed.ncbi.nlm.nih.gov/41931585/

[33] Mihaljević D, Sitaš Z, Hanulak J et al. Cerebral Toxoplasmosis in a Renal Transplant Recipient-A Rare Complication. Life (Basel). 2026. https://pubmed.ncbi.nlm.nih.gov/41900989/

[34] Jesuthasan J, Merritt K, Solmi F et al. The association between childhood Toxoplasma gondii, psychotic experiences and grey matter volume: A population-based cohort study. Schizophr Res. 2026. https://pubmed.ncbi.nlm.nih.gov/41643571/

[35] Karacali B, Mor N. Investigation of anti-Toxoplasma gondii antibody seropositivity and possible risk factors in women with abortion or stillbirth history in Kars, Turkey. Afr J Reprod Health. 2026. https://pubmed.ncbi.nlm.nih.gov/42202767/