Studies of Prevalence and Subtypes of Blastocystis Species in Lagos, Nigeria.

Blastocystosis is an emerging parasitic infection of man that is grossly unreported in our community. Studies were carried out on normal individuals and HIV/AIDS infected individuals. A total of 1207 stool samples made up of 748(62%) females and 459(38%) males were obtained from individuals attending LUTH and CMUL-PEPFAR/APIN clinics in Lagos and were analyzed by wet mount and iodine stained preparation for the detection of ova and parasites. FECT concentrate smears were also stained with trichrome chromotrope and modified Kinyoun’s acid fast stains to differentiate cysts of protozoan and oocysts of coccidian parasites. An overall prevalence of 19.2% was obtained for Blastocystis spp. among the study participants. Protozoan parasites detected include: Giardia lamblia 90(7.5%), Entamoeba histolytica/ dispar complex 48(4.0%), Cryptosporidium spp. oocysts 26(2.2%), Cyclospora cyatanensis 47(3.6%) and Isospora belli 1(0.1%). Helminthes detected were Ascaris lumbricoides 40(2.5%), Ancylostoma duodenale 29(2.4%), Fasciola spp. 10(0.8%), Hymenolepis nana 9(0.8%), Strongyloides stercoralis 12(1.0%), and Trichuris trichuria 12(1.0%). Poly-parasitism, occurred in 5(0.4%) of the overall samples examined. Prevalence of infection in females were more than the males but not statistically significant, (p> 0.05). Diarrhoea was found to be statistically associated with Blastocystis detection (p< 0.05). Age groups, sex, marital status, stool and reason for visiting the clinic showed no statistically significant association with the Blastocystis detection (p> 0.05). A total of 270 and 315 stool samples collected from HIV/AIDS individuals and non-HIV/AIDS individuals respectively were also analyzed for Blastocystis spp. and other intestinal parasites with the methods described above. Prevalence of Blastocystis spp was statistically significant among HIV/AIDS individuals 48(17.8%) compared with 30(9.5%) non-HIV/AIDS individuals(p< 0.05). Blastocystis occurred in 23.5% of the diarrhoea stool samples, with 10(9.3%) detected in non-diarrhoeal samples. Diarrhoea status and nature or consistency of stool samples were found statistically significant with Blastocystis detection in HIV positive subjects (p< 0.05). Patient’s age group, sex, and marital status were not statistically associated with the parasite detection (p> 0.05). DNA was extracted from 48 stool samples positive for Blastocystis; randomly selected from 24 each of asymptomatic and symptomatic HIV/AIDS subjects and amplified by PCR method using Blastocystis-specific primers targeting the SSUrRNA gene and sequenced. Twenty-three (48%) of the samples were positive for Blastocystis by direct PCR; comprising of 10 and 13 stool samples from asymptomatic and symptomatic individuals respectively. The sequenced Blastocystis genome revealed the presence of 3 out of the 9 subtypes (STs) described for humans, namely: STI 10 (41.6%), ST3 10(41.6%) and ST4 3(12.6%) however one isolate was not amplified. All three subtypes were identified among the symptomatic diarrheic individuals, however, ST1 was the most commonly occurring strain found among the symptomatic diarrhea HIV/AIDS participants. ST2 was not identified; ST3 was common among the asymptomatic individuals while ST4 occurred only among the symptomatic individuals. The molecular phylogenetic classes of the 22 Blastocystis isolates from Lagos metropolis were inferred using the nine known subtype, ST1- ST9 nucleotide sequences and the stored nucleotide sequences of all the known Blastocystis species stored in the GenBank of the NCBI and a tree was constructed, employing Proteromonas lacerate as an out group. Direct extraction of Blastocystis DNA from stool samples is a confirmation of the existence of the parasite in Lagos. Identification of Blastocystis subtypes 1, 3 and 4 from symptomatic diarrhoeal HIV/AIDS individuals suggest potential for pathogenicity. There is urgent need to create awareness among the health workers, particularly, clinicians and the medical laboratory scientists, who are directly involved with the laboratory identification of pathogens, before meaningful intervention can be instituted. The role of these intestinal parasitic organisms and Blastocystis species in HIV/AIDS subjects emphasized the need for differential diagnosis of diarrhea using molecular markers.
A Thesis Submitted to the School of Postgraduate Studies, University of Lagos.
Blastocystosis , Infection , HIV/AIDS , Parasitic Organisms , Research Subject Categories::MEDICINE::Microbiology, immunology, infectious diseases
Onuoha, E.S.U (2014), Studies of Prevalence and Subtypes of Blastocystis Species in Lagos, Nigeria. A Thesis Submitted to University of Lagos School of Postgraduate Studies Phd Thesis and Dissertation, 164pp.