A Survey of Cryptosporidium Species and Giardia duodenalis in Natural Water Sources in Khung Bang Kachao, Samut Prakan Province, Thailand

Abstract

Intestinal waterborne protozoa typically cause diarrhea and persist as a public health problem. Cryptosporidium spp. and Giardia duodenalis are mostly found in natural water sources, especially in agricultural areas. The transmission of Cryptosporidium spp. and G. duodenalis occurs by ingesting (oo)cysts either by the fecal-oral route or via feces-associated contamination. These parasites can be found in both humans and animals. To date, there have been many reports of Cryptosporidium spp. and G. duodenalis contamination in many areas of Thailand, such as natural ponds, rivers including Bang Pu recreational center (Brackish water) and Chao Phraya River, the main river of central Thailand.  Khung Bang Kachao is one of the reserved areas that was formed by the curving of the Chao Phraya River. All canals in Khung Bang Kachao are connected within the area and the water goes in and out by sluices which depend on the tide of Chao Phraya River. As a result, the water inside this area could possibly collect dirt or contamination which may cause a waterborne protozoa epidemic. This led the researchers to question whether the water source in this area could possibly have Cryptosporidium spp. and G. duodenalis contamination and subsequently affect human health. Therefore, this research study aimed to determine the prevalence of Cryptosporidium spp. and G. duodenalis in natural water sources in Khung Bang Kachao, Samut Prakan Province, Thailand.

The water sampling collection sites were chosen by using a purposive sampling technique. From March to July 2020, 40 samples of surface water were collected from 29 of 47 canals in six sub-districts. The temperature and pH of all collected samples were measured at the collection sites. A total of 20L per sample was filtered using a cellulose acetate membrane. Sucrose flotation and sedimentation were used to concentrate oocysts of Cryptosporidium spp. and cysts of G. duodenalis, respectively. The suspension was made for cell lysis by five cycles of freezing and thawing followed by DNA extraction of the suspension. The researchers applied molecular techniques, namely Nested PCR targeting at 18S rRNA and gdh gene for Cryptosporidium spp. and G. duodenalis, respectively. Temperature and pH were not different in each sample.

The study site was located near households, and the surrounding area was quite dirty and malodorous. Interestingly, only one sample (2.5%) of G. duodenalis was positive from Bon canal in Bang Kachao sub-district. No Cryptosporidium spp. were found in this study. A previous study showed a high prevalence of Cryptosporidium spp. in the rainy season, but unfortunately sample collection was not performed throughout the year. Moreover, the study site was not an agricultural area with the presence of animal hosts that serve as reservoir for infection. Community volunteers routinely maintained water sources by cleaning the dirt and monitoring cleanliness. So, the contamination may be very low. As a result, natural water in this area is clean and can be used for watering plants and vegetables.

The results of this study could form the basis of a database for protozoa surveillance systems in the natural water sources in Khung Bang Kachao, Samut Prakan Province. However, the presence of potential sample collection sites in unreachable or inaccessible areas was a limitation in this study. Also, the volume of water samples may need to be increased to raise the chance of waterborne protozoa detection in future studies. Routine monitoring of waterborne pathogens could be performed to assess the risk for populations, as well as to maintain the quality of natural water sources and the quality of life of life of people in the nearby communities.