Dr. Alexander Morrill on Toxomplasmosis

TOXOPLASMOSIS (Toxoplasma gondii) 

Life cycle of T. gondii: After ingestion by a host, oocysts (found in feces) and tissue cysts (found in muscle/CNS) transform into tachyzoites which localize in muscle and CNS. Tachyzoites develop into tissue cyst bradyzoites which can 

survive indefinitely in muscle/brain. Cysts are typically 10-70 microns across and do not show up on imaging. 

Signs and symptoms of acute infection: In healthy adults: no symptoms or mild, flulike symptoms + swollen lymph nodes (neck, chin, armpits, groin), usually only one lymph node swollen In infants and immunocompromised individuals: encephalitis, necrotizing retinochorioditis) 

Diagnosis: Several tests based on seropositivity are available. 

Why is this interesting? 

suspected of causing psychiatric morbidity 

infection. Worldwide prevalence is about 50% (higher in some areas, including Latin America and Middle East) Seropositivity indicating latent infection with T gondii (positive IgG titer) correlates with a broad variety of psychiatric illnesses including schizophrenia, bipolar disorder, OCD. Odds ratio for schizophrenia for individuals with latent infection : 2.73 vs. toxo-negative (2.1-3.6 CI)[Yolker). Positive IgG titer also correlated with suicide attempts in a large sample of pregnant Danish women (n=45,271) (Postolache 2013] Acute infection (positive IgM titer) is an independent risk factor for acute 

exacerbation of schizophrenia in some studies (Monroe 2015] 

cat urine has also been observed experimentally in humans with latent T. gondii infection-- but only among males [Flegr 2011] 

ondii seropositivity correlates with a remarkable number of psychological findings-prolonged reaction times, greater risk of traffic accidents, changes in personality characteristics such as suspiciousness or novelty-seeking (often with different results in women vs. men). Also may be associated with changes in testosterone and dopamine levels. 

Route of infection is by contact with fecal oocysts or tissue cysts. 

Contact with cat/mouse/bird feces 

- undercooked meat esp. pork, lamb, venison - unwashed vegetables (contaminated with soil) - raw/undercooked seafood 

- unpasteurized milk, especially goat's milk 

If mother is infected with T. gondii, treatment reduces the risk of transmission to fetus. 


Effective anti-toxo agents include TMP/SMX (for prophylaxis) or pyrimethamine (for acute infection) Once encysted, T. gondii becomes very antibiotic-resistant. Nothing is proven to eliminate cysts in humans, although some regimens have been successful in mice and partly effective in humans (e.g. atovaquone). Certain psychotropic medications are known to inhibit T. gondii growth. Ford [2015] provides a list of psychotropics with known anti-toxoplas (TATA+) vs. those without (TATA-). 

TATA+: fluphenazine, haloperidol, loxapine, paliperidone, risperidone, thioridazine, valproate (also: cyamemazine, levomepromazine, zucloptnhixol) 

TATA-: amisulpride, aripiprazole, carbamazepine, clozapine, lamotrigine, lithium, olanzapine, quetiapine, tiapride 

Implications for treatment of psychiatric disorders: 

treatment for seropositive schizophrenics. All four were negative studies. It has been speculated that this is because the treatments given were not effective against cysts. [Chorlton 2017] One study indicated that in bipolar individuals who are seropositive for toxoplasmosis, TATA+ agents led to slightly better outcomes than TATA agents. This was not true for schizophrenics, however. [Fond 2015]

Dr. Alexander Morrill

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Joel has spent his life and career pursuing greater knowledge, understanding, and treatment of the human condition. His resume reflects over twenty years’ experience.