Which component of blood can transmit Toxoplasma?

Toxoplasma Transmission in Blood Components

Toxoplasma gondii can be transmitted through leukocytes in blood, making white blood cells the primary blood component that transmits toxoplasmosis. 1

Transmission Through Blood Components

• Toxoplasma gondii primarily circulates in the blood through leukocytes (white blood cells), which can harbor the parasite and facilitate its transmission through blood transfusion 1, 2
• Studies have demonstrated that both monocytes and polymorphonuclear leukocytes can contain viable Toxoplasma organisms, though monocytes appear to be more permissive to parasite survival 3
• The tachyzoite form of Toxoplasma gondii is the stage that can be transmitted through infected blood components 4

Epidemiology of Transfusion-Transmitted Toxoplasmosis

• The overall weighted prevalence of Toxoplasma exposure in blood donors worldwide is approximately 33%, with significant regional variation 1
• The highest seroprevalence rates are observed in Africa (46%) and certain countries like Brazil (75%) and Ethiopia (73%) 1
• In some regions of Mexico, seroprevalence rates of 13.5% have been reported, with 21.8% of seropositive donors also having evidence of acute infection (IgM antibodies) 2

Pathophysiology of Blood-Borne Transmission

• After entering the bloodstream, Toxoplasma gondii parasites primarily infect leukocytes, which can then disseminate the infection throughout the body 5
• Studies have shown that greater than 80% of freshly isolated human peripheral blood monocytes and 50% of polymorphonuclear leukocytes can harbor the parasite, though they typically attempt to destroy the intracellular organisms 3
• In immunocompromised hosts, particularly those with deficient interferon-gamma responses, parasitemia can be more pronounced with higher parasite loads in circulating leukocytes 5

Risk Factors and Prevention

• Blood donors with certain risk factors, including contact with soil (OR 9.7) and consumption of undercooked meat (OR 2.5), have significantly higher rates of Toxoplasma seropositivity 4
• Tobacco use has been associated with increased seropositivity to Toxoplasma in blood donors (OR 2.09) 2
• Current blood screening methods do not routinely test for Toxoplasma gondii, and positive serology alone cannot effectively identify infectious donors since seroprevalence is high in many regions 1

Clinical Implications

• Toxoplasma transmission through blood transfusion is particularly concerning for immunocompromised recipients, including HIV-infected individuals 6
• In HIV-infected patients, toxoplasmosis can cause severe manifestations including encephalitis, pneumonitis, hepatitis, and cardiomyopathy 6
• Congenital toxoplasmosis can result from maternal infection during pregnancy, with the risk of transmission increasing with gestational age 6
• Pregnant women with evidence of primary infection or active toxoplasmosis should be evaluated in consultation with appropriate specialists 7

Common Pitfalls and Caveats

• Relying solely on serological testing for screening blood donors may be ineffective due to high seroprevalence in some populations 1
• The presence of IgG antibodies alone does not necessarily indicate active infection or infectiousness 1
• Leukoreduction of blood products may reduce but not eliminate the risk of Toxoplasma transmission 5
• The risk of transfusion-transmitted toxoplasmosis may be underestimated due to lack of routine testing and the often asymptomatic nature of acute infection 2, 4