Something on Scrub Typhus
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Dr L Bina Chanu
Contd from previous issue
These chiggers serve as both the biological vector and the primary natural reservoir for the bacteria Orientia tsutsugamushi that produce the infection. Leptotrombidium mites thrive in a specific, micro-environment often described as a ‘mite island’ They heavily populate transition zones between forests and cleared spaces, such as low-lying grasses, jungle clearings, riverbanks, forest fringes, abandoned agricultural land, and bushy weeds. They prefer high humidity, moisture, and shade, completely avoiding direct sunlight. Their habitats closely align with the nesting areas of small wild rodents (like field rats) and shrews, which serve as their preferred animal hosts.
The morphological appearance of the mite shifts depending on its developmental stages. The size of an adult mite is usually between 1.0 - 2.0 mm and are visible with the eyes but the size of the chigger larvae usually falls in the range of 015-0.3 mm which is barely visible to our eyes. The colour of the adult mite is bright red or reddish brown while that of the larval stage is pale orange, yellow or bright red. The adult mites have four pairs of legs while the chigger larvae have three pairs of legs. The body shape of the adult is like a Hourglass or figure 8-shaped body with a distinct constriction in the middle, heavily covered in velvety hairs while the shape of chigger is oval and covered with sensory hairs known as setae. The mouth parts of the adults are adapted only for soft insect eggs while that of chiggers are equipped with bladelike chelicerae to pierce the host skin and suck the fluids.
The Leptotrombidium mite undergoes seven distinct stages of development. The entire cycle generally takes about 2 to 3 months to complete. The adult females lays their fertilized eggs in moist, shaded soil or loose-leaf litter.
(To be contd)
Contd from previous issue
These chiggers serve as both the biological vector and the primary natural reservoir for the bacteria Orientia tsutsugamushi that produce the infection. Leptotrombidium mites thrive in a specific, micro-environment often described as a ‘mite island’ They heavily populate transition zones between forests and cleared spaces, such as low-lying grasses, jungle clearings, riverbanks, forest fringes, abandoned agricultural land, and bushy weeds. They prefer high humidity, moisture, and shade, completely avoiding direct sunlight. Their habitats closely align with the nesting areas of small wild rodents (like field rats) and shrews, which serve as their preferred animal hosts.
The morphological appearance of the mite shifts depending on its developmental stages. The size of an adult mite is usually between 1.0 - 2.0 mm and are visible with the eyes but the size of the chigger larvae usually falls in the range of 015-0.3 mm which is barely visible to our eyes. The colour of the adult mite is bright red or reddish brown while that of the larval stage is pale orange, yellow or bright red. The adult mites have four pairs of legs while the chigger larvae have three pairs of legs. The body shape of the adult is like a Hourglass or figure 8-shaped body with a distinct constriction in the middle, heavily covered in velvety hairs while the shape of chigger is oval and covered with sensory hairs known as setae. The mouth parts of the adults are adapted only for soft insect eggs while that of chiggers are equipped with bladelike chelicerae to pierce the host skin and suck the fluids.
The Leptotrombidium mite undergoes seven distinct stages of development. The entire cycle generally takes about 2 to 3 months to complete. The adult females lays their fertilized eggs in moist, shaded soil or loose-leaf litter.
(To be contd)