Environmental and molecular studies of Anopheles balabacensis and its associated Plasmodium parasites in Northern Sabah

Benny Obrain Joseph Manin (2019) Environmental and molecular studies of Anopheles balabacensis and its associated Plasmodium parasites in Northern Sabah. Doctoral thesis, Universiti Malaysia Sabah.

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Abstract

Malaria is still a major public health issue especially in Africa, Southeast Asia and the Eastern Mediterranean region with an estimated half a million deaths recorded annually. In 2016, an estimated of USD2.7 billion was spent on malaria elimination and control programmes globally by governments of the affected countries and the international partners. The cost is expected to increase to USD6.5 billion per year by 2020. Plasmodium knowlesi is the fifth malaria parasite that can cause malaria to humans and has emerged in the Southeast Asia region. The reservoir hosts are the non-human primates and it is transmitted to human by Anopheles mosquitoes of the Leucosphyrus group. The majority of the malaria cases reported in Malaysia are caused by knowlesi malaria especially in Sabah and Sarawak. These two states have the most P. knowlesiinfections with more than 1,200 cases reported in 2016. In Sabah, the most affected areas are located in the interior, west coast and Kudat Divisions. Despite high prevalence of P. knowlesi malaria incidence in Sabah, limited information is available regarding the mosquito vector Anopheles balabacensis. This study was conducted to gain more information about the mosquito vector in Sabah and had five objectives. The first objective was to investigate the effect of habitat types on the abundance and biting times of An. balabacensis by comparing five common habitat types in Kudat district. The second objective was to investigate the contribution of peri-domestic transmission to the risk of zoonotic malaria infection in humans in order to find out where and when people get exposed to An. balabacensis. The third objective was to study the genetic variation in subpopulations of An. balabacensis to gain an insight into the population genetics and inter-population movement in Sabah. The fourth objective was to study the phylogenetic relationship among the common Anopheles species found in Sabah in order to know how they are related to Anopheles species of same series or group found in other parts of Malaysia and other countries. The last objective was to study the phylogenetic relationship of simian Plasmodium species infecting An. balabacensis, humans and the long-tailed macaques in order to determine their genetic relationship. Sampling of Anopheles was carried out using human landing catch (HLC) method for 12 hours from 6 pm to 6 am. The specimens caught were identified to the species level based on morphological characteristics. The presence of malaria parasites in the Anopheles specimens was detected using polymerase chain reaction (PCR) assay. Generalized Linear Mixed Model (GLMM) was constructed to test variation in the abundance of An. balabacensis between habitat types and households. Mitochondrial variation of An. balabacensis was determined using the nucleotide sequence of cytochrome oxidase c subunit I (COi), cytochrome oxidase c subunit II (COil) and the combined sequence (COi and COIi). Phylogenetic tree was inferred using maximum likelihood and Bayesian methods conducted using MEGA7 software and MrBayes v3.2 program, respectively. Results of first objective indicate that abundance of An. balabacensis was not affected by habitat types. Anopheles balabacensis shows a significant different in biting time except between early night and late night. Results of second objective indicate that An. balabacensis was significantly more abundant in the peri-domestic settings than inside houses, and also higher at case than control households (0.28 ± 0.194 vs. 0.17 ± 0.127, p<0.001). The results of third objective show that mitochondrial variation of An. balabacensis was high within subpopulations as compared to between subpopulations. Tajima's D and Fu's Fs tests showed that the population is experiencing population expansion and growth. Results of fourth objective indicate that Anopheles specimens from Sabah have high nucleotide identity (>86%) with nucleotide sequences deposited in NCBI database. Anopheles balabacensis in Sabah has a same cluster with An. balabacensis in Kalimantan, Indonesia but produced a separate cluster with An. balabacensis in Central Java and West Lombok, Indonesia. Results of the last objective indicate that P. knwo/esi has 99.7% - 100.0% nucleotide identity among the isolates from An. balabacensis, human patients and a long-tailed macaque from the same locality. In conclusion, this study has provided new information regarding the An. balabacensis in Sabah. This mosquito species is dominant among species of Anopheles and was involved in the transmission of P. knowlesi in Sabah especially in the northern part. It is hoped that the information obtained in this study will be useful for future research and for helping in the planning of malaria prevention and control programs in Sabah.

Item Type:	Thesis (Doctoral)
Keyword:	Malaria, Plasmodium knowlesi, Anopheles balabacensis, Zoonotic malaria, Sabah, Malaysia Genetic variation,
Subjects:	Q Science > QR Microbiology > QR1-502 Microbiology
Department:	FACULTY > Faculty of Medicine and Health Sciences
Depositing User:	DG MASNIAH AHMAD -
Date Deposited:	11 Apr 2025 11:19
Last Modified:	11 Apr 2025 11:19
URI:	https://eprints.ums.edu.my/id/eprint/43470

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