Toxoplasmosis in Cats: Risks to Pregnant Women and Immunocompromised Individuals

Etiology and Parasite Biology

Toxoplasma gondii is an obligate intracellular apicomplexan parasite that infects virtually all warm-blooded vertebrates, with felids serving as the definitive hosts [1]. The parasite life cycle comprises both sexual and asexual phases. Sexual reproduction (gametogony) occurs exclusively within the feline intestinal epithelium, culminating in the shedding of unsporulated oocysts in feces [2]. Following sporulation (1-5 days in the environment), oocysts become infectious to intermediate hosts, including humans and livestock [3]. A single cat can excrete millions of oocysts during primary infection, making environmental contamination a key driver of transmission [2].

The pre-sexual and sexual stages of T. gondii in the feline gut have been characterized using single-cell transcriptomics, revealing distinct merozoite and gametocyte populations [2]. Recent work using retinal epithelial cells and intestinal organoids has further elucidated the differentiation pathways leading to sexual commitment [4]. Microneme protein MIC17A has been identified as a potential marker for both entero-epithelial stages and chronic tissue cysts, offering new targets for diagnostic detection of feline infections [5].

Three main clonal lineages (Types I, II, III) predominate in North America and Europe, though diverse genotypes circulate globally [6]. Strain virulence varies considerably; for instance, Type II strains are commonly associated with human congenital toxoplasmosis, while atypical strains may cause severe ocular disease [7, 8].

Epidemiology

Feline seroprevalence of T. gondii varies widely by geographic region and management practices. In Hong Kong, seroprevalence in privately-owned cats was 12.3% versus 23.7% in community cats [9]. A study in Jordan reported seroprevalence of 45.1% with associated risk factors including outdoor access and raw meat feeding [10]. In stray cats from Bangkok, Thailand, PCR-based detection of T. gondii DNA in feces yielded a prevalence of 7.8% [11]. In Poland, wild felids showed lower seroprevalence (4.0%) compared to domestic cats [12]. Urban informal settlements in Brazil demonstrate high exposure in both cats and other domestic animals due to environmental degradation and social marginalization [3, 13].

Risk factors for feline infection include unrestricted outdoor roaming, consumption of raw or undercooked meat, hunting behavior, and contact with contaminated soil [9, 10]. The AB blood group phenotype in cats does not appear to influence susceptibility to infection [14].

Transmission to humans occurs primarily through ingestion of sporulated oocysts from contaminated soil, water, or produce; consumption of tissue cysts in undercooked meat; and rarely via blood transfusion [15, 16]. Vertical transmission is a major concern for pregnant women; primary infection acquired during gestation can result in congenital toxoplasmosis, leading to abortion, stillbirth, or neonatal disease [17, 16]. The risk of fetal infection increases with gestational age, but severity decreases [16]. Seroprevalence studies in women with histories of abortion or stillbirth in Turkey revealed significantly higher anti-T. gondii antibody positivity compared to controls [17]. In Côte d'Ivoire, pregnant women exhibited knowledge gaps regarding toxoplasmosis transmission and prevention [18].

Immunocompromised individuals, including organ transplant recipients, patients with malignancies, and those with sickle cell disease, are at elevated risk for reactivation of latent toxoplasmosis [15, 19, 20]. Cerebral toxoplasmosis is a rare but severe complication in renal transplant recipients [19]. Seropositivity in patients with malignancies in Iran reached 39.2% [20]. Ocular toxoplasmosis can occur in both immunocompetent and immunocompromised individuals, with reactivation of retinochoroidal lesions being more common in the latter [7, 8].

Clinical Signs and Pathology in Cats

Feline toxoplasmosis often remains subclinical. When disease occurs, clinical signs are typically associated with the acute phase of infection, during which tachyzoites undergo rapid replication in host cells [21]. Common presentations include fever, lethargy, anorexia, and respiratory distress due to pneumonitis. Ocular signs such as uveitis, chorioretinitis, and anterior chamber inflammation are observed [7]. Neurological manifestations can include seizures, ataxia, and behavioral changes [22]. Hepatic and pancreatic involvement may lead to icterus and vomiting.

Pathologically, necrotic foci are found in multiple organs, particularly the lungs, liver, spleen, and lymph nodes. Histological examination reveals tachyzoites and tissue cysts, with associated mononuclear cell infiltration. The intestinal stages in the definitive host cause transient enteritis, but most cats clear entero-epithelial infection without overt diarrhea [2].

Cat Toxoplasmosis Baby: Zoonotic Risk to Pregnant Women

The phrase "cat toxoplasmosis baby" encapsulates the public health concern that pregnant women may acquire toxoplasmosis from their pet cats and transmit the parasite to the developing fetus. This risk must be contextualized: the primary source of human infection is not direct contact with cats but rather ingestion of oocysts from environmental contamination or consumption of undercooked meat [16]. Cats only shed oocysts for a brief period (1-3 weeks) following primary infection, and reinfection generally does not lead to renewed shedding [9]. Proper hygiene, such as daily litter box cleaning (before oocysts sporulate), wearing gloves, and hand washing, virtually eliminates risk [16]. Nevertheless, seronegative pregnant women should avoid handling litter boxes and adopt preventive measures [18, 16].

Diagnostics

Diagnostic approaches for feline toxoplasmosis include serological, molecular, histological, and antigen-based methods.

Serology. Detection of anti-T. gondii IgG and IgM antibodies is the most common diagnostic modality. Commercial enzyme-linked immunosorbent assays (ELISAs) are widely used [23]. A double-antigen sandwich colloidal gold immunochromatographic strip has been developed and field-validated for rapid detection of antibodies across multiple host species, including cats [23]. This test utilizes recombinant antigens to achieve high sensitivity and specificity. IgG seropositivity indicates past exposure; rising titers or IgM positivity suggests recent infection [5]. MIC17A-based serological assays show promise for detecting both entero-epithelial and chronic stage infections [5].

Molecular detection. Conventional and real-time PCR assays targeting the B1 gene or 529-bp repetitive element are standard for detecting T. gondii DNA in tissues, blood, and feces [24]. An antisense PCR assay has been developed specifically for domestic cats, improving sensitivity for low-level parasitemia [24]. Fecal PCR can differentiate active oocyst shedding from past exposure [11]. PCR detection in stray cat feces in Thailand identified 7.8% positivity, demonstrating the utility of molecular surveillance for environmental risk assessment [11].

Histopathology. Tissue biopsy with histochemical staining (e.g., hematoxylin and eosin, periodic acid-Schiff) or immunohistochemistry using monoclonal anti-T. gondii antibodies can identify tachyzoites and tissue cysts in clinical specimens [25]. Histopathological detection of T. gondii in aborted fetal myocardium has been reported in goats, with analogous applications in feline pathology [25].

Antigen detection. Double-antigen sandwich immunochromatographic strips provide point-of-care detection of antibodies without species restriction [23]. Western blot analysis can confirm serological results.

Diagnostic method comparison

Treatment and Control in Cats

Treatment. The standard therapeutic regimen for acute feline toxoplasmosis consists of a combination of clindamycin (10-12 mg/kg orally every 12 hours for 2-4 weeks) or a trimethoprim-sulfonamide combination, often supplemented with folinic acid to mitigate bone marrow suppression [21]. For ocular disease, topical corticosteroids may be used in conjunction with systemic antiprotozoals to control inflammation. Clindamycin is commonly prescribed; however, resistance and tolerability concerns remain. Alternative agents include pyrimethamine plus a sulfonamide, though feline toxicity limits use.

Vaccine development. No licensed vaccine currently exists for feline toxoplasmosis. Gene-edited live-attenuated vaccines (e.g., T. gondii strains with deletion of essential virulence genes) represent a promising avenue, inducing protective immunity while preventing reversion to virulence [21]. Advances in mRNA vaccine technology and One Health strategies are being explored for both veterinary and human applications [26]. Pre-sexual stage antigens are potential targets for blocking oocyst shedding [1].

Control measures. Prevention of feline toxoplasmosis centers on management practices:

• Feed cats only commercial cooked or canned food to prevent ingestion of tissue cysts [9].
• Prevent hunting and scavenging by keeping cats indoors [9, 10].
• Clean litter boxes daily; dispose of feces in sealed bags.
• Pregnant women and immunocompromised individuals should avoid litter box duties [16].
• Reduce environmental contamination through proper disposal of cat feces.
• Stray cat population management reduces oocyst contamination in high-risk areas [11, 10].

Mermaid decision tree for feline toxoplasmosis diagnosis and management

flowchart TD
    A[Cat with suspected toxoplasmosis], > B[Serology: ELISA IgG/IgM]
    B, > C{Acute infection?}
    C, >|IgM positive or rising IgG| D[PCR on blood/feces]
    D, > E[Positive], > F[Start clindamycin therapy]
    D, > G[Negative], > H[Consider other causes]
    C, >|IgG only, low titer| I[Chronic infection - no treatment unless clinical signs]
    C, >|Clinical signs present| J[Tissue biopsy or PCR]
    J, > K[Positive], > F
    J, > L[Negative], > M[Re-evaluate diagnosis]
    F, > N[Recheck serology/PCR after therapy]
    N, > O[Resolution], > P[Preventive management: indoor, cooked food]
    N, > Q[Persistent], > R[Switch antiprotozoal or investigate resistance]

Prevention flowchart for pregnant women and immunocompromised individuals

flowchart LR
    A[Owner at risk: pregnant or immunocompromised], > B{Owns a cat?}
    B, >|Yes| C[Cat indoor-only, fed cooked food]
    C, > D[Owner avoids litter box]
    D, > E[Daily litter cleaning by another person]
    E, > F[Wear gloves and wash hands if unavoidable]
    F, > G[Serological testing of cat if unknown status]
    G, > H[If cat seronegative, maintain prevention]
    G, > I[If cat seropositive, no additional risk if no active shedding]
    B, >|No| J[General prevention: cook meat thoroughly, wash produce]

Conclusion

Toxoplasma gondii infection in cats is a significant zoonotic concern for pregnant women and immunocompromised individuals due to the potential for congenital transmission and severe disease. The risk can be effectively managed through education, proper hygiene, and veterinary preventive care. Advances in diagnostics, including antisense PCR and multi-species immunochromatographic strips, enable more accurate detection of infection in cats. Continued research into vaccines and strain epidemiology will further refine control strategies. A One Health approach integrating veterinary, medical, and environmental health is essential for reducing the burden of toxoplasmosis globally [26].

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. URL: 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. URL: https://pubmed.ncbi.nlm.nih.gov/42020723/

[3] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42330015/

[4] Cancela S, Sena F, Pagotto R, et al. Enhancing pre-sexual and sexual differentiation of Toxoplasma gondii using retinal epithelial cells and intestinal organoids. Cell Rep. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41108686/ *** 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.

[5] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41874672/

[6] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41528989/

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

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

[9] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42135800/

[10] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41741047/

[11] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42094705/

[12] Didkowska A, Kołodziej-Sobocińska M, Matusik K, et al. Toxoplasma gondii in wild felides in Poland. BMC Vet Res. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41387866/

[13] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41401226/

[14] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41471183/

[15] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41931585/

[16] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41628830/

[17] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42202767/

[18] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42199683/

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

[20] Roya SK, Maryam ER, Ahmad H, et al. Investigation of the Prevalence of Toxoplasmosis in Patients with Malignancies, Southwest of Iran. Arch Razi Inst. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41179623/

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

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

[23] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42253330/

[24] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41724116/

[25] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41864556/

[26] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42188907/

[27] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42201205/

[28] 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. URL: https://pubmed.ncbi.nlm.nih.gov/42020619/

[29] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41965856/

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

[31] 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. URL: https://pubmed.ncbi.nlm.nih.gov/41651631/

[32] Villa-Mancera A, Vargas-Tizatl E, Robles-Robles JM, et al. High Seroprevalence of Toxoplasma gondii and Neospora caninum Infections Among Goats in Mexico Is Associated with Climatic, Environmental, and Risk Factors. Pathogens. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41305406/

[33] Jacquart A, Blake DP, Spiro S, et al. Occurrence and characterisation of Toxoplasma gondii infection in free-living Eurasian beavers, Castor fiber, from southern England. Sci Rep. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41290903/

[34] Pielok Ł, Sałamatin R, Swarcewicz J, et al. Toxocarosis, toxoplasmosis and ocular dirofilariasis diagnosed in a polish farmer from Wielkopolska Voivodeship - a case description. BMC Ophthalmol. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41225401/

[35] Alani AAJ, Omar TM. Epidemiology and Risk Factors of Ovine Toxoplasmosis: Evidence from a Cross-Sectional Study in Iraq. Acta Parasitol. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41148433/