Detection of Orientia tsutsugamushi in Novel Trombiculid Mite Species in Northern Tamil Nadu, India: Use of Targeting the Multicopy traD Gene

Detection of Orientia tsutsugamushi DNA in a trombiculid mite chigger species suggests that it might be a potential vector of scrub typhus in an endemic area. Over a period of 20 mo, 85 rats were trapped, 57 had chiggers that were identified by standard morphometric techniques. The chigger pools were assessed by performing PCR assays targeting fragments of the single-copy genes 56 kDa type-specific antigen gene (TSA56) by nested PCR and the 47 kDa (htrA) quantitative real-time PCR (qPCR). The novel traD SYBR green assay that detects a multicopy gene was also performed. In total, 27 chigger pools were positive by traD qPCR, of which only 7 were positive by 47 kDa qPCR and in 3 of these, 56 kDa gene was amplified by nested PCR. Orientia tsutsugamushi-specific DNA was detected in Ascoschoengastia spp., Schoengastiella ligula, Leptotrombidium rajasthanense, Leptotrombidium deliense, and Leptotrombidium jayawickremei chigger pools. Therefore, they could be potential vectors of scrub typhus in Southern India. The three 56 kDa sequences belonged to TA716 genotype and Kato genogroup. Further studies are needed to confirm these chigger species as scrub typhus vectors in Northern Tamil Nadu.

Stylostome of the trombiculid mite larvae Neotrombicula talmiensis (Schluger, 1955) (Acariformes, Trombiculidae) feeding on two host species in the Russian Far East

Stylostome and skin inflammatory reaction during feeding of Neotrombicula talmiensis (Schluger, 1955) (Acariformes, Trombiculidae) larvae on the naturally infected host animals – voles Myodes rufocanus Sundevall, 1846 and Asian chipmunk Tamias sibiricus (Laxmann, 1769) were studied by histological methods. In addition, larvae were studied in scanning electron microscope (SEM). The apical hypostomal portions form a temporal sucker, which applies to the host skin during feeding. Larval feeding on both naturally infected voles and chipmunks causes an epidermal hyperkeratosis and a permanent delayed inflammation with predominance of neutrophil leukocytes, dilation of dermal capillaries and local hemorrhages. Larvae tend to feed in tight groups and may attach themselves to both ‘living’ epidermis and hypertrophic stratum corneum. The stylostome is organized nearly identically in the two host species, which points to the species-specific character of the feeding tube in trombiculid larvae. The stylostome does not penetrate the epidermis through, so it may be classified as belonging to the epidermal type. The stylostome is produced by a solidifying larval secretion and composed of the proximal eosinophil cone and the main stylostome tube, both pale-pink in azure-II-eosin with a greyish peripheral portion more pronounced in voles. No longitudinal and transverse stratification is found in the stylostome composition. In contrast with other trombiculid larvae studied so far, larvae of N. talmiensis also ingest, besides liquefied nutrients, a pure blood that reveals a possibility for trombiculid larvae to be natural bloodsuckers.

A CASE SERIES ON SCRUB TYPHUS

Scrub typhus is a rickettsial disease caused by Orientia tsutsugamushi. It is transmitted to humans via infected chiggers (larva of trombiculid mite). Eschar is a characteristic feature for the diagnosis of scrub typhus and other mite or tick-borne rickettsiosis. Immunofluorescence Antibody (IFA) test is the gold standard for the diagnosis, and doxycycline is the drug of choice for treatment of scrub typhus. We present a case series of scrub typhus in three patients from South India. All three patients presented with high grade fever and IgM scrub typhus was positive status in all cases. Doxycycline 100 mg twice daily for 7 days along with supportive care was effective in all the cases. Serum creatinine levels dropped to normal and renal status of all patients improved well with antimicrobial treatment. Early diagnosis of the infection is necessary as the disease as it can have multiple system involvement and serious complications.

Scrub Typhus in Western Nepal: A Series of Case Reports

Scrub typhus, a mite borne infectious disease which is transmitted to humans by bite of trombiculid mite. An eschar, which is a characteristic necrotic skin lesion, is formed at the site of bite. Systemic spread via the hematogenous and lymphatic routes occur and the infected people develop fever, cutaneous rash, myalgia, and lymphadenopathy. Diagnosis of scrub typhus is often difficult because of vast variability and non-specific presentation of the disease. Scrub typhus has been poorly reported from Kaski district. Here we report series of five cases of scrub typhus from Kaski distrist of Western Nepal.

Ectoparasite extinction in simplified lizard assemblages during experimental island invasion

Introduced species can become invasive, damaging ecosystems and disrupting economies through explosive population growth. One mechanism underlying population expansion in invasive populations is ‘enemy release’, whereby the invader experiences relaxation of agonistic interactions with other species, including parasites. However, direct observational evidence of release from parasitism during invasion is rare. We mimicked the early stages of invasion by experimentally translocating populations of mite-parasitized slender anole lizards ( Anolis apletophallus ) to islands that varied in the number of native anoles. Two islands were anole-free prior to the introduction, whereas a third island had a resident population of Gaige's anole ( Anolis gaigei ). We then characterized changes in trombiculid mite parasitism over multiple generations post-introduction. We found that mites rapidly went extinct on one-species islands, but that lizards introduced to the two-species island retained mites. After three generations, the two-species island had the highest total density and biomass of lizards, but the lowest density of the introduced species, implying that the ‘invasion’ had been less successful. This field-transplant study suggests that native species can be ‘enemy reservoirs’ that facilitate co-colonization of ectoparasites with the invasive host. Broadly, these results indicate that the presence of intact and diverse native communities may help to curb invasiveness.

Scrub typhus: as it stands today

Scrub typhus is one of the three most common causes of prolonged fever in Southeast Asia and Pacific affecting almost 1 million people annually worldwide out of 1 billion exposed. Scrub typhus is a rickettsial infection caused by Orientia Tsutsugamushi transmitted through bite of Chiggers (larval stage of trombiculid mite). It is an acute febrile illness which generally causes non-specific symptoms and signs. The clinical manifestations of this disease range from sub-clinical disease to organ failure and death. Deaths are attributable to late presentation, delayed diagnosis, and drug resistance. Scrub typhus, though endemic in India; yet is under reported. It should be considered as an important differential diagnosis in a febrile patient with thrombocytopenia, deranged liver or renal functions, and B/L chest opacities. Relapse is not uncommon. Presumptive treatment with Doxycycline can be a suitable option in febrile patients from Typhus pockets. Alert physician should keep an eye on deviation from usual presentation to changing spectrum of the disease. Early diagnosis and appropriate treatment is rewarding and prevents morbidity and mortality.