Species composition and activity patterns of sand flies (Psycodidae: Phlebotomine) in four tehsils of Dir Districts, Khyber Pakhtunkhwa, Pakistan

Epidemiology of cutaneous leishmaniasis in children of Khyber Pakhtunkhwa, Pakistan

OBJECTIVES

In Pakistan, cutaneous leishmaniasis is an emerging tropical disease and a very high number (>70%) of children are afflicted by this marring infection. This study aimed to scrutinise the prevalence, spatial distribution and socio-demographic and behavioural risk factors associated with cutaneous leishmaniasis in children aged <5-15  years in Khyber Pakhtunkhwa.

METHODS

A total of 1, 559 clinically confirmed records of children diagnosed with cutaneous leishmaniasis (January-December) from 2020 and 2022 were obtained from selected district hospitals. In addition, a risk factors-related questionnaire was administered to 1, 011 households (400 in 2020 and 611 in 2022) in nine districts during a household survey.

RESULTS

The maximum number of cutaneous leishmaniasis cases was recorded in 2022 (n = 877, 56.25%) as compared to 2020 (n = 682, 43.75%). The hospital records showed a greater number of male patients in the 2022 cohort (n = 603, 68.76%). The highest number of cases were observed in children aged 5-9 years in 2022 (n = 282, 32.16%) and 2020 (n = 255, 37.39%). In 2020 and 2022, cutaneous leishmaniasis cases showed peak aggregation in March (n = 118, 17.3%) and January (n = 322, 36.72%). From a spatial analysis, the maximum number of cutaneous leishmaniasis cases was recorded at 59-1700 m elevation in various land-use/land-cover and climatic regions with quaternary alluvium rock formations. A multivariate logistic regression model analysis of risk factors from the households survey suggested that age group, socio-economic status, construction materials of the house, use of insect repellents, Afghan refugee camps in the village/district, knowledge and biting times of sand flies, frequent use of mosquito bed nets, presence of domestic animals in the house, knowledge of the transmission period and peak month of leishmaniasis infection increased the risk of acquiring cutaneous leishmaniasis (p  value < 0.05).

CONCLUSION

Our analysis demonstrated that cutaneous leishmaniasis in children is influenced by a variety of environmental, socio-demographic and behavioural risk factors in Khyber Pakhtunkhwa. The increase in recorded cases of cutaneous leishmaniasis in children in 2022 compared to 2020 suggests that the infection likely extended to new foci in the province.

Environmental and socio-demographic factors associated with cutaneous leishmaniasis in district Khyber, Pakistan; alarming spread of the disease to new foci

Cutaneous leishmaniasis (CL) is a sand fly-borne infection of significant public health concern in Pakistan (endemic for CL). This study aimed to scrutinize the environmental and socio-economic risk factors for CL in district Khyber (located on Pak-Afghan border), Pakistan. Clinically confirmed 2881 CL case records for (January-December) 2017 and 2020 were obtained from district hospital. In addition, a questionnaire for CL risk factors assessment was administered to 525 households (175 in 2017 and 350 in 2020) in 40 villages throughout the district in a household survey. Higher number of CL cases were recorded in 2020 (N = 1824 belonging to 90 villages) compared to 2017 (N = 1057 from 42 villages). Highest number of CL patient cases were recorded in tehsil Jamrud (N = 2248, 39.01 %), followed by Landi Kotal (N = 398, 6.91 %) and Bara (N = 235, 4.08 %). Records showed higher number of CL cases in males (N = 1,659, 57.58 %) compared to females (N = 1,222, 42.41 %). In 2017 and 2020 the disease burden peaked in January. GIS-based spatial analyses of hospital records revealed that CL cases were abundant at 294-1,916 m elevation, in agriculture and range lands. Univariate logistic regression model analysis of risk factors suggested that higher education, family size >15, knowledge of CL, having family member/s that suffered from CL in the past, knowledge about biting time of sand flies, use of mosquito spray, presence of Afghan refugees in the village/s and living in mud-made houses increased the risk of acquiring CL. The multivariable logistic regression model showed none of the risk factors to be statistically significant. Findings of the study are crucial towards effective and targeted control of CL in district Khyber.

Sand fly bionomics, geospatial investigation and risk factors associated with cutaneous leishmaniasis in district Mardan, Pakistan

The present investigation was designed in response to the 2019 outbreak of cutaneous leishmaniasis (CL) in 34 villages of district Mardan, Pakistan. Sand flies were collected to study their bionomics, breeding sites, and seasonal prevalence from July to September 2019. In 2020, we acquired and digitized data on CL patients in the region to assess the possible spread of the disease to new foci. In the study period, a total of 1572 sand flies were collected, comprising 11 species. Phlebotomus sergenti (827, 52.61%) was the most widespread species. The soil pH in all samples was slightly alkaline (7-8.2) and potassium (K) was the richest component (59.4%). In 2020, there were 975 reported cases, which is an increase from 536 cases in 2019. Elevations of 361-588 m, agricultural land near human settlements, and quaternary alluvium formation had maximum CL cases. In univariate analysis, age between 25 and 35, nationality, family size (7-15 individuals), knowledge of leishmaniasis, site of infection, family members suffering from leishmaniasis, knowledge of sand flies, the difference between mosquitoes and sand flies, biting times of sand flies, use of mosquito spray, an Afghan refugee in the region, preachers visiting, and material of house construction have been identified risk of getting CL (p < 0.05). In stepwise multivariate analysis, nationality, vegetation, site of infection, and material of house construction were more prone to CL (p < 0.05). This study highlights the potential risk factors and sand flies associated with the outbreak of CL in Mardan. The high abundance of P. sergenti suggests their possible role as vectors for the transmission of CL in the region. The increase in reported cases in 2020 compared to 2019 suggests a possible spread of the disease to new foci. The study also revealed that certain demographic and environmental factors were significant risk factors for contracting CL in the district.

Distribution and Risk of Cutaneous Leishmaniasis in Khyber Pakhtunkhwa, Pakistan

Cutaneous leishmaniasis (CL) is a zoonotic infection caused by obligate intracellular protozoa of the genus Leishmania. This study aimed to investigate CL in Khyber Pakhtunkhwa, Pakistan and to estimate the risk of epidemics. Clinico-epidemiological data of 3188 CL patients were collected from health facilities in 2021. Risk factors were analyzed using the chi-square test. ArcGIS V.10.7.1 was applied for spatial analysis. The association between CL occurrence and climatic variables was examined by Bayesian geostatistical analysis. The clinical data revealed males or individuals younger than 20 years old were more affected. Most patients presented with a single lesion, and the face was the most attacked body part. CL was prevalent in the southern region in winter. A proportional symbol map, a choropleth map, and a digital elevation model map were built to show the distribution of CL. Focal transmission was predicted by inverse distance weighting interpolation. Cluster and outlier analysis identified clusters in Bannu, Dir Lower, and Mardan, and hotspot analysis suggested Bannu as a high-risk foci. Bayesian geostatistical analysis indicated that increasing precipitation and temperature as well as low altitudes were associated with CL infection. The study has provided important information for public health sectors to develop intervention strategies for future CL epidemics.

Sand Flies (Diptera: Psychodidae): Fauna and Ecology in the Northeast of Algeria

Sand flies (Diptera: Psychodidae) transmit several Leishmania (Kinetoplastida: Trypanosomatidae) species, which cause leishmaniasis, a significant public health concern in Algeria. We compared sand fly species abundance and composition among different biotopes (urban, peri-urban, rural areas), bioclimatic zones (humid, sub-humid, semi-arid), and elevation ranges. We also used the additive partitioning of beta diversity to test whether the variation in sand fly composition among biotopes, bioclimatic zones, and elevation ranges is due to species turnover or community subsetting. In total, 7,478 specimens were captured; of which, 7,162 (51.5% males vs. 48.5% females) belong to eight species: Phlebotomus perniciosus Newstead, 1911 (77.4% of the total captured specimens), Phlebotomus perfiliewi Parrot, 1930 (14.6%), Phlebotomus longicuspis Nitzulescu, 1911 (5.9%), Phlebotomus papatasi Scopoli, 1786 (<1%), Phlebotomus sergenti Parrot, 1917 (<1%) and Phlebotomus chadlii Rioux, Juminer et Gibily 1966 (<1%), Sergentomyia minuta Adler et Theodor, 1927 (1%), and Sergentomyia fallax Parrot, 1921 (<1%). Sand fly total abundance showed negative correlations with altitude and was significantly higher in rural areas. Sandfly community composition was significantly different between rural and urban/peri-urban areas. The additive partitioning of beta diversity showed that 71.4% of the compositional dissimilarity among elevation ranges and bioclimates was due to sand fly species turnover, and 28.6% resulted from nestedness. However, the variation in sand fly composition among different biotopes was mainly due to community nestedness. Findings from this study help define the risk of Leishmania transmission and develop methods for vector control in Mila province and Algeria as a whole.

Characterization of sand fly breeding sites in district Malakand, Khyber Pakhtunkhwa, Pakistan, and evaluation of risk factors for cutaneous leishmaniasis in the region

Present study was carried to determine the sand fly species composition, breeding sites ecology, seasonal abundance, and spatial distribution in district Malakand, Khyber Pakhtunkhwa, Pakistan. In addition, risk factors associated with cutaneous leishmaniasis (CL) were also evaluated. Survey of indoor and outdoor habitats was carried out using sticky traps in 31 villages of Dargai and Batkhela tehsils of Malakand. Soil from habitats of adult and immature sand flies was analysed. Questionnaire-based household survey was also performed in these villages to assess risk factors associated with CL. Soil samples from selected CL positive households were analysed for its contents. Additionally, clinicoepidemiological data from local health centres was examined for the year 2019. Total of 3,140 sand flies belonging to 18 species were collected. Phlebotomus sergenti was the most abundant species (38.16%). Its abundance had a strong positive correlation with mean monthly relative humidity and negative correlation with average temperature. Phlebotomus sergenti and Phlebotomus papatasi were abundant at an elevation ranging from 320 to 1,120 m above sea level and in agricultural lands near human settlements. Flight height preference apparatus collected maximum sand flies at 30 cm (1ft) above the ground and all species associated negatively with height. Soil analysis from habitats of adult and immature flies showed that highest mean number of adults and immatures were recorded from silt loam which carried highest concentrations of K₂ O, Mg, Ca, and Zn. Number of immature sand flies correlated moderately (r = .7, p < .05) with K₂ O soil concentrations. There was significant similarity between organic matter contents in soil samples from positive breeding sites and CL households (Wilcoxon rank-sum test, p = .1976). In multivariate analysis model for CL risk factors, age (26-35 and >35 years), knowledge of leishmaniasis, living in a middle and upper class, preachers visit to villages, and assumption that Afghan refugees are more prone to CL were significant. CL patient's archived data from health centres showed that majority of patients had lesions on face and hands. Patient's influx was highest in February and March.

SYSTEMATIC REVIEW OF LEISHMANIASIS IN PAKISTAN: EVALUATING SPATIAL DISTRIBUTION AND RISK FACTORS

Both cutaneous (zoonotic cutaneous leishmaniasis [ZCL] and anthroponotic cutaneous leishmaniasis [ACL]) and visceral leishmaniasis (VL) are prevalent in Pakistan, although the cutaneous form is comparatively more widespread. The present study aimed to spatially map different forms of leishmaniasis in Pakistan. In addition, the risk for acquiring leishmaniasis was assessed in different locations of the country. Previously published literature on leishmaniasis distribution and associated risk factors in Pakistan was obtained from PubMed/NCBI and GoogleScholar using specific keywords. Further, 50 articles that focused on geographical distribution and risk factors of the disease in Pakistan were obtained and systematically reviewed. Data regarding location (used in ArcGIS for spatial analysis), number of cases, and risk factors were identified. The present study revealed a high burden of cutaneous leishmaniasis in the northern and western foci of Pakistan. Leishmania major, chiefly a causative agent of ZCL, was observed to be prevalent in the arid and semi-arid climatic zones of the country with elevations between 45 and 2,837 m (maximum number at low elevation). Leishmania tropica cases, associated with ACL, were recorded at elevations ranging from 551 to 2,837 m (majority cases at high elevation). Visceral leishmaniasis (VL) (reportedly caused by Leishmania infantum) was sporadically distributed in the northern areas at elevations 1,432-2,873 m. For VL, particularly, mountainous communities, farming communities, and the presence of dogs were the most commonly reported risk factors. On the other hand, poor preventive measures, migration, presence of domesticated animals, presence of cattle dung, living in mud houses, and outdoor sleeping habits were the principal risk factors associated with cutaneous leishmaniasis (CL). This investigation can guide the health experts and medical entomologists toward targeted and cost-effective surveillance and control of leishmaniasis in Pakistan.

Sand Fly (Diptera: Psychodidae) Species Diversity, Habitat Preferences, and Ecological Aspects of Distribution in Bajaur District, Khyber Pakhtunkhwa, Pakistan

The species composition, distribution, and bionomics of sand flies was investigated from January to December 2017 in four tehsils (20 villages) of district Bajaur (formally Bajaur agency), Khyber Pakhtunkhwa, Pakistan. In total, 4,173 adult specimens comprising of seven species of Phlebotomus (Diptera: Psychodidae) and three species of Sergentomyia (Diptera: Psychodidae) were collected by oral aspirator, insecticide spray, and sticky traps from June to October. Highest numbers of flies were collected indoors in July and August when relative humidity and temperature were highest. Phlebotomus sergenti Parrot (Diptera: Psychodidae) was the most abundant species from all the collection sites, making approximately 70% of the total capture. Combined dwellings and chicken cages harbored the highest number of adult and immature flies (unrotated external genitalia). Abundance of P. sergenti had a significant (P ≤ 0.05) positive correlation with monthly average temperature, relative humidity, and average rainfall in indoor collections. On the other hand, P. papatasi Scopoli displayed similar correlation in the indoor and nighttime collections. Both the species were apparently abundant in the elevation range ≤ 419 m above sea level and on rangelands. Phlebotomus papatasi, however, also occurred on agricultural lands. The number of cutaneous leishmaniasis (CL) cases did not significantly correlate with the abundance of sand fly vectors across the villages surveyed. The results reported herein can serve as a baseline for an all-extensive future work in Bajaur. Our investigations will benefit the public health experts and medical entomologists for improved control and surveillance vectors of leishmaniasis.

Cutaneous leishmaniasis in male schoolchildren in the upper and lower Dir districts of Khyber Pakhtunkhwa, and a review of previous record in Pakistan

Documented reports are limited, showing cutaneous leishmaniasis (CL) as a severe threat to schoolchildren in Pakistan. The present study aimed to investigate the clinico-epidemiology and associated risk factors of CL in local and Afghan male schoolchildren between 6 and 16 years of age. The experimental strategy involved a questionnaire for the collection of information and clinical diagnosis (microscopy and semi-nested PCR) of 113 CL symptomatic schoolchildren out of 8,833 schoolchildren (7,175 local and 1,658 Afghan refugees) studying in nineteen schools of the Upper and Lower Dir Districts, Khyber Pakhtunkhwa, Pakistan. Previous records of CL in Pakistan was studied, and spatial analysis was performed on elevation and agro-ecological maps using Arc-GIS v10.3.1. Active lesions were found predominant (n=113, 1.2%: cutaneous lesions, 97, 86%, and lesions with mucosal involvement, 16, 14%) than scars (20, 0.25%). Active lesions of both local (100, 88%) and Afghan refugees (13, 12%), and infected age groups were found significantly different. Majority of the lesions were dry crusted (98, 86.7%), single (83, 73%), and frequently infecting facial region (59, 52%). Avoiding bed nets, living in mud houses and animal shelters were highly associated with CL infection. Temergara (30, 26.5%) and Rabath (14, 12.3%) were hyperendemic CL foci. Microscopically, 71 (63%) cases were positive, while the PCR assay revealed Leishmania tropica in 110 (97.3%) cases. Previous record revealed that L. tropica is dominant throughout Pakistan, and dry mountains and plateaus of northwestern and southwestern regions are spatially at high-risk. Measures should be taken to reduce CL infection by eliminating the associated risk factors, promoting PCR-based diagnosis and basic medical facilities.

Phlebotomine sand flies and Leishmania species in a focus of cutaneous leishmaniasis in Algeria

Cutaneous leishmaniasis is a disease caused by various Leishmania spp., which are transmitted by phlebotomine sand flies. Algeria is one of the most affected countries, with thousands of cutaneous leishmaniasis cases registered every year. From March to November of 2016 and 2017, sand flies were collected in 12 municipalities in Setif province, North-Eastern Algeria. Sand flies were identified and females were tested by PCR for detecting Leishmania DNA. Additionally, cutaneous leishmaniasis cases notified during the study period were analysed. Out of 1804 sand flies collected, 1737 were identified as belonging to seven species, with Phlebotomus perniciosus (76.2%), Ph. papatasi (16.7%) and Ph. sergenti (5.0%) being the most common species, representing together 97.9% of the collected specimens. The remaining specimens were identified as Sergentomyia minuta, Se. fallax, Ph. longicuspis and Ph. perfiliewi. The number of sand flies collected monthly was positively correlated with temperature. Out of 804 females tested, nine Ph. perniciosus (1.1%) scored positive for Leishmania infantum (n = 5), L. major (n = 3) and L. tropica (n = 1), respectively. During the study period, 34 cutaneous leishmaniasis cases were notified in Setif, of which 58.8% were patients residing in two urban and peri-urban municipalities and 41.2% in rural areas. The finding of Ph. perniciosus as the most abundant species in Setif suggests that this sand fly may be adapted to different biotopes in the North-East region of Algeria. The detection of different Leishmania spp. in Ph. perniciosus suggests a complex epidemiological picture of cutaneous leishmaniasis in Setif, with the involvement of different etiological agents and possibly with different reservoir hosts and vectors.

Leishmaniasis is a group of neglected diseases, with more than 350 million people at risk and 2 million new cases every year. Leishmania parasites are transmitted by phlebotomine sand flies. Algeria is one of most affected countries, with thousands of cutaneous leishmaniasis cases registered every year. However, in spite of the scientific knowledge gained over the last decades, the understanding of the biology and the ecology of sand flies in some areas of Algeria is still fragmentary. The present study was conducted from 2016 to 2017 to assess the sand fly population in Setif and also the Leishmania spp. circulating in this province. Our data suggest a complex epidemiological picture of cutaneous leishmaniasis in Setif, with the involvement of different etiological agents and possibly with different reservoir hosts and vectors.

Habitat characterization of sand fly vectors of leishmaniasis in Khyber Pakhtunkhwa, Pakistan

Leishmaniasis is currently prevalent in 98 countries including Pakistan, where its wide-spread. Phlebotomus papatasi Scopoli and Phlebotomus sergenti Parrot are suspected vectors of cutaneous leishmaniasis (CL) while P. Phlebotomus major Yakimoff and Phlebotomus hindustanicus Theodor are vectors of visceral leishmaniasis (VL) in the Khyber Pakhtunkhwa (KP) province of Pakistan. The present study identifies the complexity of environmental factors affecting the distribution of these vector sand fly species in KP. Sand fly habitats in the province were characterized from relevant published sources and analyzed using geographic information system (GIS) tools. Specific spatial analysis indicated that P. sergenti and P. papatasi were ecological generalists, found in diverse ecological settings, while P. major and P. hindustanicus were less frequent and had restricted foci in Khyber Pakhtunkhwa. We specifically observed a close association between elevation and existance of several sand fly species. P. sergenti primarily presented at high elevation while P. papatasi had distribution at low altitudinal ranges. P. major and P. hindustanicus were apparently limited to high altitudes in the northern areas of the province. This GIS-based spatial investigation of Phlebotomine vectors of leishmaniasis aims to provide a beneficial tools to medical entomologists, epidemiologists and public health workers for regional control of leishmaniasis. Outcomes from such spatial studies can be utilized in planning vector control initiatives so as to ensure proper allocation of funds for the region's integrated vector control program budget.

Geospatial and Climatic Patterns Associated With the Distribution of Sand Fly (Diptera: Psychodidae) Vectors of Leishmaniasis in Pakistan

We provide a comprehensive and updated review on the effects of elevation and climatic factors on distribution of sand fly (Diptera: Psychodidae) vectors of cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) across Pakistan. Our study was undertaken in view of the increasing risk of leishmaniasis, particularly resulting from climatic deviations and political instability in the region. Literature (published and unpublished) on suspected vectors of CL (Phlebotomus sergenti Parrot and Phlebotomus papatasi Scopoli) and VL (Phlebotomus major Yakimoff and Schokhor and Phlebotomus hindustanicus Theodor) was collected, sorted, and utilized in geospatial analysis. P. papatasi and P. sergenti co-occurred in majority of the referenced localities and were generally distributed toward the western and southern parts across a wide range of elevation, whereas P. major and P. hindustanicus were limited to high elevation in cool and humid northern areas of Pakistan. Conversely P. papatasi and P. sergenti exploited diverse ecological settings across the country, being particularly abundant in warm/hot and arid regions.

Potential Resting and Breeding Sites of Sand Flies (Diptera: Psychodidae) and Their Habitat Characteristics in Leishmaniasis Foci of Dir Districts, Khyber Pakhtunkhwa, Pakistan

Despite their medical importance, natural breeding sites of sand flies have been poorly explored. Detecting such sites is imperative in vector control strategies. This study aimed to identify potential breeding and resting microhabitats of sand flies and household risk factors associated with cutaneous leishmaniasis transmission in Dir districts, Khyber Pakhtunkhwa, Pakistan. Survey of indoor and outdoor habitats in four tehsils (subdistricts) of upper and lower Dir districts was carried out using sticky traps, flit method, and aspirator. To assess risk factors associated with cutaneous leishmaniasis (CL), questionnaires were administered to household heads. Mud houses and plants belonging to Cucurbitaceae family sheltered highest number of sand flies. Excessive number of flies were collected from indoor sites (common rooms used for both people and animals) compared to outdoor habitats (cattle dungs). Phlebotomus salangensis Artemiev, 1978 and Phlebotomus sergenti were the most widely distributed species, while Sergentomyia bailyi peaked in caves with high organic content in soil. Roof material and ownership of fans were associated with significant risk of CL. Findings of this study present a list of potential breeding sites for sand flies and CL risk factors that can be targeted and implemented in control programs for CL. Further studies are required to elucidate the breeding behavior and preferences of these medically important vectors.

Environmental risk modelling and potential sand fly vectors of cutaneous leishmaniasis in Chitral district: a leishmanial focal point of mount Tirich Mir, Pakistan

OBJECTIVE

To provide baseline information about suspected vectors and the incidence, distribution and an active zone of transmission for cutaneous leishmaniasis (CL) in Chitral, Pakistan, using GIS tools; and to investigate the role of environmental factors in the disease dynamics.

METHOD

Two surveys in 2014 and 2016 as a basis for choropleth and environmental risk mapping.

RESULTS

A total of 769 captured specimens yielded 14 Phlebotomus and six Sergentomyia species including two potential vectors of CL, i.e. Phlebotomus papatasi and Phlebotomus sergenti. P. papatasi (71%) was dominant, followed by P. sergenti (18%). A choropleth map generated in Arcmap 10.1 based on 1560 CL case reports displayed maximum prevalence (0.92-2.5%) in Ayun, Broz, Charun, Chitral 1 and 2 and Darosh 1 and 2 union councils. An environmental risk map constructed by MaxEnt 3.3.3 defined an active zone of transmission based on leishmaniasis occurrence records (n = 315). The analysis of variable contribution in MaxEnt indicates significance of elevation (54.4%), population density (23.3%) and land use/land cover (6.6%) in CL disease dynamics.

CONCLUSION

The probability of CL increases (0.6-1 on logistic scale) in severely deforested areas, in lowland valleys and in regions with high-population density.