An initial survey of 150 horses from Thailand for anti-Pythium insidiosum antibodies.

INTRODUCTION: Pythium insidiosum causes a life-threatening infection termed pythiosis in humans and other animals. The organism has been identified in tropical and subtropical environments worldwide. Since 1985, human pythiosis has been increasingly reported from Thailand. Seroprevalence studies estimated that 32,000 Thai people had been exposed to the pathogen. In 2018, the first animal pythiosis case in Thailand was diagnosed in a horse. Here, we investigated the seroprevalence of anti-P. insidiosum antibodies in the Thai equine population. MATERIALS AND METHODS: We surveyed serum anti-P. insidiosum antibodies in 150 horses distributed across Thailand, using three established serological tests: enzyme-linked immunosorbent assay (ELISA), immunochromatographic test (ICT), and Western blot analysis. RESULTS: ELISA detected the anti-P. insidiosum antibodies in three horses. ICT and Western blot confirmed the presence of the antibodies in one of the ELISA-positive horses. Based on one positive out of 150 horses tested, the seroprevalence of anti-P. insidiosum antibodies in the Thai equine population was 0.7%, which is markedly higher than that in the Thai human population (0.07%), but much lower than that in the Brazilian equine population (11.1%). CONCLUSION: The seroprevalence of the anti-P. insidiosum antibodies in the equine population suggests a higher incidence of pythiosis in horses than in humans. The antibody surveillance reported by our group was undertaken to promote a better understanding of the epidemiology and host susceptibility of pythiosis in Thailand.

Protein A/G-based enzyme-linked immunosorbent assay for detection of anti-Pythium insidiosum antibodies in human and animal subjects.

OBJECTIVES: Pythiosis is a deadly infectious disease caused by Pythium insidiosum. Reports of both human and animal pythiosis are on the rise worldwide. Prognosis of the pythiosis patients relies on early diagnosis and prompt treatment. There are needs for an immunodiagnostic test that can detect the disease in both humans and animals. This study aims at reporting an optimized protocol for the development of a protein A/G-based enzyme-linked immunosorbent assay (ELISA) for the detection of anti-P. insidiosum antibody in multiple host species. RESULTS: A total of 25 pythiosis and 50 control sera, obtained from humans, horses, dogs, cats, and cows, were recruited for the assay development. With a proper ELISA cutoff point, all pythiosis sera can ultimately be distinguished from the control sera. The successfully-developed protein A/G-based ELISA can detect the anti-P. insidiosum antibodies in serum samples of both humans and animals. It is a versatile, feasible-to-develop, and functional immunodiagnostic assay for pythiosis.

Monitoring Anti-Pythium insidiosum IgG Antibodies and (1→3)-ß-d-Glucan in Vascular Pythiosis.

Despite aggressive treatment, vascular pythiosis has a mortality rate of 40%. This is due to delays in diagnosis and a lack of effective monitoring tools. To overcome this drawback, serum beta-d-glucan (BG) and P. insidiosum-specific antibody (Pi-Ab) were examined as potential monitoring markers in vascular pythiosis. A prospective cohort study of vascular pythiosis patients was carried out from January 2010 to July 2016. Clinical information and blood samples were collected and evaluated by the BG and Pi-Ab assays. Linear mixed-effect models were used to compare BG and Pi-Ab levels. The in vitro susceptibility test was performed with all P. insidiosum isolates from culture-positive cases. A total of 50 patients were enrolled: 45 survived and 5 died during follow-up. The survivors had a significantly shorter time to medical care (P < 0.0001) and a significantly shorter waiting time to the first surgery (P < 0.0001). There were no differences in BG levels among the groups at diagnosis (P = 0.33); however, BG levels among survivors were significantly lower than those of the deceased group at 0.5 months (P < 0.0001) and became undetectable after 3 months. Survivors were able to maintain an enzyme-linked immunosorbent assay (ELISA) value (EV) of Pi-Ab above 8, whereas the EV among deceased patients was less than 4. In vitro susceptibility results revealed no synergistic effects between itraconazole and terbinafine. This study showed that BG and Pi-Ab are potentially valuable markers to monitor the disease after treatment initiation. An unchanged BG level at 2 weeks after surgery should prompt an evaluation for residual disease.

Insights into the pathophysiology of iron metabolism in Pythium insidiosum infections.

Pythium insidiosum causes life-threatening disease in mammals. Animals with pythiosis usually develop anemia, and most human patients are reported to have thalassemia and the major consequence of thalassemia, iron overload. Therefore, this study evaluated the iron metabolism in rabbits experimentally infected with P. insidiosum. Ten infected rabbits were divided into two groups: one groups received a placebo, and the other was treated with immunotherapy. Five rabbits were used as negative controls. The hematological and biochemical parameters, including the iron profile, were evaluated. Microcytic hypochromic anemia was observed in the infected animals, and this condition was more accentuated in the untreated group. The serum iron level was decreased, whereas the transferrin level was increased, resulting in low saturation. The level of stainable iron in hepatocytes was markedly decreased in the untreated group. A high correlation was observed between the total iron binding capacity and the lesion size, and this correlation likely confirms the affinity of P. insidiosum for iron. The data from this study corroborate the previous implications of iron in the pathogenesis of pythiosis in humans and animals.