Several other medical arthropods in southern of Vietnam (Ticks, chigger mites, and gamasid mites)

Study on medical arthropod is limited in Vietnam, some investigations have shown that medically important arthropods include ticks, chigger mites, gamasid mites and fleas which are relatively common in many regions of Vietnam. The Institute of Malariology - Parasitology - Entomology in Ho Chi Minh City conducted surveys to identify species composition and distribution of several medical arthropods in southern Vietnam and assessing for the presence of pathogens for humans and animals.

Fig 1. Diagram of survey sites

1. Ticks:

Ticks are excellent vectors for disease transmission; consequently, tick-borne diseases are common. Ticks can carry and transmit a remarkable array of pathogens, including bacteria, spirochetes, rickettsiae, protozoa, viruses, nematodes, and toxins. A single tick bite can transmit multiple pathogens, a phenomenon that has led to atypical presentations of some classic tick-borne diseases.

Some diseases are caused by tick bites: Rickettsial diseases (spotted fever and Q fever), Tick-borne encephalitis, Crimean-Congo hemorrhagic fever, Lyme disease, Relapsing fever (borreliosis), Tularaemia…

There are 81 species were found in Vietnam. In this study we have identified species composition of ticks (Ixodoidea) and the present of human pathogens present on ticks in south Vietnam, as follows:

The species composition of ticks (Ixodoidea):

Ixodoidea has 2 families, 6 genus, 9 species: Argas sp., Amblyomma sp., Aponommacrassipes, Aponommagervaisi, Haemaphysalis (H.) yeni, Ixodes (Ixodes) granulatus, Rhipicephalus (Boophylus) microplus, Rhipicephalus (Rhipicephalus) haemaphysaloides, Rh. (Rh.) sanguineus.
The dominant species in the area were Rhipicephalus (Rhipicephalus) sanguineus, Rhipicephalus (Boophylus) microplus and distributed in all survey sites
Ticks were mainly parasitic on cows, dogs, python.

Fig 2. Tick species in southern of Vietnam

Fig 3. The host of tick in southern of Vietnam

The present of human pathogens present in ticks:

The analysis of 1,846 tick samples (9,182 individuals) of 9 ticks species by PCR and RT-PCR:

+ All tick samples were negative for DNA of O. tsutsugamushi, Coxiella burnetii, Rickettsia prowazekii, Rickettsia mooseri

+ All tick samples were negative for RNA of the Bunyaviridae (Orthobunyavirus, Nairovirus, Phlebovirus).

+ There were 6/1,846 tick samples which were positive for DNA of Rickettsia spp. (0.3%). They were Rhipicephalus (Rh.) sanguineus that parasitic on domestic dogs (Canisfamiliaris).

2. Chigger mite:

Trombiculid mites (Acari: Trombiculidae) are distributed worldwide ectoparasites of a wide range of vertebrates. More than 50 species are known to bite humans, and about 20 have medical importance. The larval stages (chiggers) of the genus Leptotrombidium are vectors of Orientia tsutsugamushi, causative agent of scrub typhus. This life-threatening disease is widely endemic in Asian Pacific regions where more than one billion people are at risk of acquiring the infection and around one million new cases are estimated to occur annually. In addition, although underreported and often misdiagnosed, trombiculiasis, defined as a dermatitis caused by the salivary secretion of biting chiggers, is present in America and Europe

There are 99 species were found in Vietnam. In this study we have identified species composition of chigger mites (Trombiculidae) and the present of human pathogens present on chigger mites in south Vietnam, as follows:

The species composition of chigger mites (Trombiculidae):

Trombiculidae has 5 genus, 11 species: Ascoschoengastia (Laurentella) indic ;a, As. (L.) indica, Choengastia sp., Eutrombicula wichmanni, Eu. hirsti, Gahrliepia (Walchia) chinensis, G. (W.) lupella, Gahrliepia (W.) pacifica, G. (W.) parapacifica, Leptotrombidium (Leptotrombidium) deliense, L. (L.) striatum.
The dominant species in the area were G. (W.) chinensis, L. deliense, As. (L.) indica, G. lupella and distributed in most survey sites
The larva chigger mites were mainly parasitic on rats.

Fig 4. Some chigger mites in southern of Vietnam

Fig 5. Collecting chigger mite on the host

The present of human pathogens present on chigger mites:

The analysis of 830 chigger mite samples (13,763 individuals) of 11 chigger mite species by PCR and RT-PCR:

+ All chigger mite samples were negative for DNA of Coxiella burnetii, Rickettsia prowazekii, Rickettsia mooseri

+ All chigger mite samples were negative for RNA of the Bunyaviridae (Orthobunyavirus, Nairovirus, Phlebovirus).

+ There are 13/830 chigger mite samples which were positive for DNA of O. tsutsugamushi (1.57%). They were Leptotrombidium (L.) deliense, Ascoschoengastia (L.) indica, Gahrliepia (W.) parapacifica that parasitic on rats (R. norvegieus, R. edwardsi, R. rattus, R. argentiventer, R. molliculus).

3. Gamasid mite:

Gamasid mites (mesostigmatid mites) belong to the order (or suborder) Mesostigmata, subclass Acari in class Arachnida. Some gamasid mites are ectoparasites while others are predatory mites, nidicolous mites, or edaphic mites found in the hosts’nests, soil, litter, and humus. Small mammals (especially rodents) are the most common hosts for ectoparasitic gamasid mites. Besides causing such disorders as mite dermatitis, some species of ectoparasitic gamasid mites are transmitting vectors of rickettsialpox and hemorrhagic fever with renal syndrome (HFRS).

There are 71 species were found in Vietnam. In this study we have identified species composition of gamasid mites (Gamasoidea) and the present of human pathogens present on gamasid mites in south Vietnam, as follows:

The species composition of gamasid mites (Gamasoidea):

Gamasoidea has 4 families, 5 genus, 14 species: Haemolelaps zuluensis, Laelaps (Echinolaelap) aingworthae, L. (E.) echininus, L. (E.) sanguisugus, L. (E.) sedlaceki, L. (E.) traubi, Laelaps (Laelaps) nuttalli, Lealaps (L.) myonyssognathus, Laelaps (L.) prognathous, L. (L.) tainguyeni, Dermanyssus sp., Macrocheles glaber, Ornithonyssus bacoti, Or. bursa.
The dominant species in the area were Laelaps (E.) echininus, L. (E.) sanguisugus, L. (E.) sedlaceki, Ornithonysus bursa, Or. bacoti and distributed in most survey sites.
Gamasid mites were mainly parasitic on rats and living on nest of animal