1.Evaluation of blood preservation methods in the performance of the WHO in vitro micro-test for Plasmodium falciparum in the field
Moritoshi Iwagami ; Nao Taguchi ; Ray U. Angluben ; Aleyla S. Escueta ; Elena A. Villacorte ; Pilarita T. Rivera ; Shigeyuki Kano ; Shin-ichiro Kawazu
Tropical Medicine and Health 2007;35(4):337-341
In vitro drug susceptibility testing of Plasmodium falciparum must be conducted immediately after collecting a sample of the patient‘s blood; otherwise the parasites may weaken and the culture fail. Collecting blood samples from individuals in areas far from the field station or clinic where in vitro testing is conducted requires a reliable method of sample preservation during transportation. We examined and compared three different methods used to preserve blood samples in endemic areas in the Philippines. The three methods are as follows: the on-site method (test is conducted soon after blood sampling), flask culture method (sample is taken to the laboratory in a culture flask with medium) and EDTA tube method (sample is taken to the laboratory in a blood collection tube). The WHO in vitro micro-test for susceptibility of P. falciparum to chloroquine was performed using an AnaeroPack® system and a portable thermostat incubator. Evaluation of the three methods was based on schizont maturation, ease of handling, and risk of contamination during the test. The on-site and flask culture methods, but not the EDTA tube method, were effective for keeping the parasites viable. Furthermore, schizont maturation appeared better with the flask method than with the on-site method, especially in the control wells (drug-free wells). In addition, it was easier to perform the flask method than the on-site method. No contamination was observed using any of the methods. The results of the study suggest that the flask culture method is the most effective and useful way to preserve blood samples for the in vitro test and, moreover, that it aids in providing detailed field evidence of drug-resistant malaria.
2.Infection rate of Schistosoma japonicum in the snail Oncomelania hupensis quadrasi in endemic villages in the Philippines: Need for snail surveillance technique
Fornillos, R.J.C. ; Fontanilla, I.K.C ; Chigusa, Y. ; Kikuchi, M. ; Kirinoki, M. ; Kato-Hayashi, N. ; Kawazu, S. ; Angeles, J.M ; Tabios, I.K. ; Moendeg, K. ; Goto, Y. ; Tamayo, P.G ; Gampoy, E.F ; Pates, I. ; Chua, J.C ; Leonardo, L.R
Tropical Biomedicine 2019;36(2):402-411
Schistosomiasis japonica is one of seven NTDs endemic in the Philippines that
continues to threaten public health in the country. The causative agent, the blood fluke
Schistosoma japonicum, uses an amphibious snail Oncomelania hupensis quadrasi which
can harbor larval stages that multiply asexually, eventually producing the infective cercariae
which are shed into the water. Contamination of freshwater bodies inhabited by the snail
intermediate host occurs through release of human and animal feces containing S.
japonicum eggs. Miracidia hatching from these eggs subsequently infect the snails that
inhabit these water bodies. The degree of fecal contamination can vary across snail sites
and influences snail infection rates in these sites. In this study, conventional malacological
surveys using intensive manual search for snails were conducted from 2015 to 2016 in
seven selected endemic provinces, namely Leyte and Bohol in the Visayas and Surigao del
Norte, Agusan del Sur, Bukidnon, Lanao del Norte and Compostela Valley in Mindanao. A
total of 6,279 O. hupensis quadrasi snails were collected from 38 snail sites. The
municipality of Trento in Agusan del Sur recorded the highest number of snail sites (7) that
yielded O. hupensis quadrasi snails while only one snail site was found positive for O.
hupensis quadrasi snails in Kapatagan in Lanao del Norte and Talibon in Bohol. Alegria in
Surigao del Norte yielded the highest number of snail sites (5) that were found to harbor
snails positive for S. japonicum infection. The snail infection rates in this municipality
ranged from 0.43% to 14.71%. None of the snails collected from Talibon in Bohol was
infected. Bohol is the only province among the 28 schistosomiasis-endemic provinces
which has reached near elimination status. Snail infection rates were found to vary
considerably across snail sites, which could be due to the degree of fecal contamination of
the snail sites and their connectivity to water that can serve as contamination source.