Molecular prevalence, spatial distribution and epidemiological risk factors of Plasmodium knowlesi infection among Macaca fascicularis raffles in Peninsular Malaysia
Malaria caused by the haemoparasite Plasmodium is one of the important vector-borne tropical diseases among humans and a wide variety of animals, especially in the tropical regions where the mosquito vectors are abundant. Plasmodium knowlesi is a zoonotic simian malaria parasite with the Long-tai...
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/92318/1/FPV%202020%207%20-%20IR.pdf |
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| Summary: | Malaria caused by the haemoparasite Plasmodium is one of the important
vector-borne tropical diseases among humans and a wide variety of animals,
especially in the tropical regions where the mosquito vectors are abundant.
Plasmodium knowlesi is a zoonotic simian malaria parasite with the Long-tailed
macaques (Macaca fascicularis) are the natural reservoir hosts. It is now the
most common and most fatal human malaria and is responsible for the
increasing number of human malaria cases in Malaysia. Despite of the growing
importance of zoonotic malaria, many aspects of its biology and epidemiology
especially in the natural macaque hosts remains undetermined throughout
Southeast Asia. The aim of this study was to ascertain the molecular prevalence,
spatial distribution pattern, and epidemiological risk factors associated with P.
knowlesi infection among Long-tailed macaques (Macaca fascicularis) in
Peninsular Malaysia. Blood samples from 1587 Long-tailed macaques captured
from 122 different locations in Peninsular Malaysia were subjected to
Plasmodium detection by nested PCR amplification using primers targeting the
18S SSU rRNA gene. Molecular detection revealed that 48.39% of the
macaques were positive for Plasmodium infection where P. cynomolgi was the
most prevalent (28.92%), followed by P. inui (22.94%), P. coatneyi (14.37%) and
P. knowlesi (13.55%). Analysis of Plasmodium species co-infection with P.
knowlesi revealed a higher prevalence of multiple species infection (18.10%)
compared to single P. knowlesi infection (9.90%). The multivariate regression
analysis showed that number of Plasmodium species co-infection, gender of the
macaques, spatial sampling zones and geographical location were the
significant risk factors associated with P. knowlesi infection among the
macaques. The spatial distribution pattern of P. knowlesi infection demonstrated
that the highest infection occurred in the North-west zone and West-coastal region of Peninsular Malaysia, with numerous infection hotspots having >75%
infection rates. Plasmodium knowlesi infection among the macaques was
present in all states of Peninsular Malaysia indicating the endemicity and
widespread nature of the infection. The overall analysis on the influence of host
factors on the prevalence of P. knowlesi demonstrated that the prevalence rate
was higher in the adult and juvenile macaques. The macaques sampled from
the forest habitat recorded the lowest infection rate (11.1%) compared to those
captured from the urban (14.79%), sub-urban (14.08%) and plantation (14.67%)
habitats. However, this suggested that P. knowlesi infection is not restricted to
the macaque in forest area but is also common among macaques inhabiting the
urban, sub-urban and plantation areas. Higher prevalence of infection was also
noted for the macaques sampled in habitats further away from the coast (>60km)
and those inhabiting the inland at higher elevations (>80m above sea level). The
present study constitutes the first attempt in Southeast Asia to screen a large
number of macaques and to determine the epidemiological risk factors for P.
knowlesi infection among the sylvatic macaque hosts. It is envisaged that the
findings from this study will provide a better understanding on the molecular
epidemiology and spatial distribution of this zoonotic parasite in this country and
facilitate further surveillance and control programs to be initiated. |
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