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Doctor of Philosophy in Biology

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College of Science




Rattus norvegicus and Rattus rattus mindanensis caught in agricultural (AGR), commercial (COM), and residential (RES) sites in Dasmariñas, Cavite, Philippines were serologically assayed for anti-T. gondii antibodies (Abs) using the TOXOCELL AD direct agglutination test kit (BIOKIT S.A. Manufacturing Company, Barcelona, Spain). Fifty eight percent (58.0%) of R. norvegicus and 42.0% of R. r. mindanensis were seropositive (sero+). Infection was higher in male rats, and those caught in the commercial site had 100.0% seropositivity. Thirty percent (30.0%) of the R. norvegicus and 51.0% R. rattus mindanensis had acute infection. Seventy percent (70.0%) of the R. norvegicus and 49.0% of R. rattus mindanensis were chronically infected with Abs titre 1:256-1:2048 and 1:256-1024, respectively. The association between the presence of infection with the rat gender and species and their collection sites was insignificant (p>0.05). Mice inoculated with different dosages (0.5-1.0ml BTH+) prepared from T. gondii chronically-infected rats were monitored for four weeks post-exposure (PE), and the histopathology in the lungs, liver, spleen, heart, diaphragm and brain was evaluated. Ninety three (=64.0%) of BTH+-inoculated mice were sero+. Seropositivity was significant (p≤0.05) in mice exposed to 0.75-1.0ml BTH+. Regardless of the rat species used as source of BTH+, seropositivity was significantly lower (p≤0.05) in BTH+/RES-inoculated mice relative to those exposed to BTH+/AGR and COM. Weight change per week in sero+ mice was significantly lower (p≤0.01) compared to seronegative (sero-) and control mice. Percent mortality was 11.0% in sero+ mice. Tissue damage was observed in the lungs, liver, spleen, heart, diaphragm, and brain starting Wk-1 PE. Regardless of the source of BTH+ and inoculum dose, inflammatory cell infiltration, vasculitis and blood vessel congestion and dilatation were consistently manifested in the tissues examined. Severity of damage was more pronounced in the lungs and liver than the other tissues at WK-1 to WK-2 PE. Tachyzoites were found in the blood and peritoneal exudates as well as in different organs examined as early as WK-1 PE. With the progression of infection to WK-3 and WK-4 PE, tissue damage became more evident in the spleen, heart, diaphragm and brain. Histopathologic manifestations consisted of interstitial pneumonia, atelactasis of the alveoli and pulmonary congestion due to hemorrhages; hepatic congestion, necrosis of the liver tissue and cells; hyperplasia of the macrophages, hypoplasia of the white pulp, and necrosis of the spleen; myocarditis of the heart; myositis of the diaphragm; and non-suppurative 3 meningoencephalitis, gliosis and perivascular cuffing of the brain. Tissue cysts were found in the heart, diaphragm and brain of mice exposed to R.r.m.-BTH+/RES as early as WK-3 PE. Infection in mice exposed to R. norvegicus and R. rattus mindanensis- BTH+ caught in AGR and COM sites was more severe relative to mice exposed to BTH+/RES. Rat and mouse serology and histopathology suggest the existence of avirulent/low virulent T. gondii strain infecting R. norvegicus and R. rattus mindanensis inhabiting the RES site relative to those caught in AGR and COM sites; The presence of tissue cysts in the diaphragm, heart and brain of mice exposed to BTH+/RES as early as WK-3 PE may be indicative of the avirulence/low virulence of T. gondii parasite. The source and inoculum dose of BTH+, and the duration of infection have clearly influenced the severity of histopathologic manifestations.

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Archives, The Learning Commons, 12F Henry Sy Sr. Hall


Serology; Parasites; Histology, Pathological; Infection

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