Seasonal abundance of Leptotrombidium deliense, the vector of scrub typhus, in areas reporting acute encephalitis syndrome in Gorakhpur district, Uttar Pradesh, India.

The rickettsial pathogen Orientia tsutsugamushi, causing scrub typhus, has been implicated as a major cause of acute encephalitis syndrome (AES) in many places in India including Gorakhpur district of Uttar Pradesh. Seasonal abundance of the principal vector mite of the pathogen, Leptotrombidium deliense, its animal hosts, and prevalence of infection on them are important attributes in the assessment of outbreaks of the disease. Hence, these aspects were investigated, seasonally, in rural villages of Gorakhpur district, where peak incidence of AES cases were reported. A total of 903 animals (rodents/shrews) was collected using 6484 Sherman traps in eight study villages (14% overall trap rate). A sum of 5526 trombiculid mites comprising 12 species was collected from 676 live rodents/shrews screened. Suncus murinus, the Asian house shrew was the predominant species (67%). Among trombiculids, the principal vector mite, L. deliense, was predominant (64.7%) and its infestation index (i.e., average number of chiggers per host animal) was 5.3. The L. deliense infestation index was higher during July to November with a peak in October. Out of 401 animal sera samples screened, 68% were positive for antibodies against O. tsutsugamushi. Of 465 blood samples tested by nested PCR, seven were positive for the 56 kDa gene of O. tsutsugamushi. In conventional PCR, 41 out of 265 samples were positive for the 60 kDa groEL gene of O. tsutsugamushi. Among the 5526 mite samples, tested as 352 pools through nested PCR, four pools were positive for 56 kDa gene. Phylogenetic analysis of 56 and 60 kDa genes confirmed circulation of Karp and TA678 (rodents) and TA678 (mite) serotypes of O. tsutsugamushi in Gorakhpur. Peak incidence of AES in Gorakhpur district occurs during the rainy season (July-October), coinciding with the peak abundance of L. deliense. These results indicate involvement of L. deliense as the vector mite transmitting the scrub typhus pathogen O. tsutsugamushi to humans in the rural areas of Gorakhpur district, India.

Heterogeneous response of Wuchereria bancrofti-infected persons to diethylcarbamazine (DEC) and its implications for the Global Programme to Eliminate Lymphatic Filariasis (GPELF).

DEC or ivermectin (IVM) in combination with albendazole (ALB) has been the recommended strategy of the Global Programme to Eliminate Lymphatic Filariasis (GPELF) since 2000. Despite effective population coverage (> 65%) with several rounds of MDA with DEC or combination of DEC plus ALB, microfilariae persist in few individuals and they continue to be the source of infection for transmitting LF. We report an individual's variability in response to DEC by defining the response as complete absence of microfilaria (mf) (post-treatment mf count = 0) and non-response as presence of mf (post-treatment mf count ≥ 1). We analyzed follow-up data on individual's response to treatment from two randomized clinical trials in which 46 microfilaremic individuals were treated with single-dose DEC (6 mg/kg body weight). They were classified into low, medium, and high mf density categories based on their pre-treatment mf counts. Of the 46 individuals, 65.2% have not responded throughout the 12-month post-treatment period. Application of a logistic regression model with fixed (age, gender, mf density, post-treatment time, and their interactions) and random (individual's response over time) effects indicated that treatment response is independent of age, gender, and time. The overall treatment response increases in low and decreases in high mf density categories. Furthermore, the estimates for the random coefficients model showed that there is a greater variability in response between individuals over post-treatment time. The results substantiate that individual variation in response to DEC exists which indicate the importance of studying the parasite as well as host genetic factors associated with DEC action.

Nonstructural protein-1 (NS1) of dengue virus type-2 differentially stimulate expressions of matrix metalloproteinases in monocytes: protective effect of paracetamol.

BACKGROUND: Dengue fever is a re-emerging viral disease and affects millions of population worldwide. Monocytes are involved in dengue viral disease, however, their exact role is still not clear. In the present study, we investigated, the effect of NS1 antigen of dengue virus and paracetamol on THP-1 monocytes associated to expressions of matrix metalloproteinases (MMPs) and cytokine release. METHODS: Assessment of cell morphology by bright field microscopy, cell viability by MTT assay, protein estimation by Bradford reagent were done in cells exposed to NS1 antigen in the presence and absence of paracetamol. Cytokines estimations were done by ELISA. Expression profile of matrix metalloproteinase genes was done using real-time PCR and reverse-transcriptase PCR. RESULTS: NS1 exposure of THP-1 monocytes cells, changed their cell morphology and activated them for release of proteins in 24 h. Expressions of MMP-2, MMP-8, MMP-9 and MMP-14 genes were upregulated by NS1 exposure. Further, exposure of NS1 to THP-1 monocytes cells increased expression profile of MMP-10 and MMP-13 genes to a lesser extent. Treatment with paracetamol (1 mg/ml and 2 mg/ml), significantly down-regulated the expression profile of MMP-2, MMP-8, MMP-9 and 14 in dose dependent manner. NS1 exposure also increased the release of cytokines IL-4, IL-6, and IL-10 but decreased the release of TNF-α and IL-15. Interestingly, paracetamol reversed NS1 induced changes in the release of these cytokine in dose dependent manner. CONCLUSION: Monocytes mediated expression of MMPs participates in the development of dengue pathogenesis in the severe cases of disease and paracetamol may have a protective effect in dengue viral disease.

Occurrence of Orientia tsutsugamushi, the Etiological Agent of Scrub Typhus in Animal Hosts and Mite Vectors in Areas Reporting Human Cases of Acute Encephalitis Syndrome in the Gorakhpur Region of Uttar Pradesh, India.

Outbreaks of acute encephalitis syndrome (AES) with high fatality and disability, are reported every year in the Gorakhpur region of Uttar Pradesh, India, with the etiology of >60% of the cases being attributed to scrub typhus. In the present study, the prevalence of Orientia tsutsugamushi, the etiological agent of scrub typhus, was investigated among animal hosts and their ectoparasitic trombiculid mites prevalent in AES-reported areas of Gorakhpur. A total of 154 rodents/shrews were collected using 777 Sherman traps set in 12 study villages, and the overall trap rate was 19.8%. In total, 2726 trombiculid mites belonging to 12 species were collected from 154 rodents/shrews trapped. The shrew mouse Suncus murinus was the predominant animal species (78.6%) collected. The principal vector mite Leptotrombidium deliense was the predominant species (82.7%), and its index was 14.6 per animal. Of 114 rodent/shrew sera samples screened through the Weil-Felix test, 57% were positive for antibodies against O. tsutsugamushi. Of 128 blood samples tested by polymerase chain reaction (PCR), one rodent sample was positive for the gene encoding 56 kDa protein and 25 for 60 kDa. Among 2726 mite samples tested as 315 pools through nested PCR, seven pools were positive for 56 kDa gene. Phylogenetic analysis confirmed circulation of Gilliam, Karp, and TA678 serotypes of O. tsutsugamushi in Gorakhpur. The study clearly demonstrated natural infection of O. tsutsugamushi in both small-animal hosts and vector mites in the AES-reporting villages of Gorakhpur, which confirms transmission of the scrub typhus pathogen in this region. The high infestation rate of L. deliense with O. tsutsugamushi infection indicates that the people living in the rural villages of Gorakhpur are at risk of infection with scrub typhus, which might lead to AES.

Entomological investigation of Japanese encephalitis outbreak in Malkangiri district of Odisha state, India.

BACKGROUND: A severe outbreak of Japanese encephalitis (JE) and acute encephalitis syndrome (AES) with high case fatality was reported from Malkangiri district of Odisha state, India during September to November 2016 affecting 336 children with 103 deaths. OBJECTIVES: The purpose of this study was to investigate the outbreak in the light of entomological determinants. METHODS: Entomological investigation was carried out in 48 villages from four mostly affected Community Health Centres (CHCs) of Malkangiri district. Dusk collections of resting adults was done in villages from indoor and outdoor sites to record the density of mosquito species, including the known JE vectors, feeding behaviour, parity, dusk index and infection status with JE virus (JEV). FINDINGS: The per man hour density and dusk index of JE vector species varied from 2.5 to 24.0 and 0.81 to 7.62, respectively in study villages. A total of 1136 mosquitoes belonging to six vector species were subjected to PCR and one pool of Culex vishnui was found to be positive for JEV. CONCLUSION: The JE transmission in Malkangiri district was confirmed. Thorough screening of human blood samples of JE/AES suspected cases and JE vector mosquitoes for the presence of JEV during rainy season every year is recommended.

Entomological investigation of Japanese encephalitis outbreak in Malkangiri district of Odisha state, India

BACKGROUND A severe outbreak of Japanese encephalitis (JE) and acute encephalitis syndrome (AES) with high case fatality was reported from Malkangiri district of Odisha state, India during September to November 2016 affecting 336 children with 103 deaths. OBJECTIVES The purpose of this study was to investigate the outbreak in the light of entomological determinants. METHODS Entomological investigation was carried out in 48 villages from four mostly affected Community Health Centres (CHCs) of Malkangiri district. Dusk collections of resting adults was done in villages from indoor and outdoor sites to record the density of mosquito species, including the known JE vectors, feeding behaviour, parity, dusk index and infection status with JE virus (JEV). FINDINGS The per man hour density and dusk index of JE vector species varied from 2.5 to 24.0 and 0.81 to 7.62, respectively in study villages. A total of 1136 mosquitoes belonging to six vector species were subjected to PCR and one pool of Culex vishnui was found to be positive for JEV. CONCLUSION The JE transmission in Malkangiri district was confirmed. Thorough screening of human blood samples of JE/AES suspected cases and JE vector mosquitoes for the presence of JEV during rainy season every year is recommended.