Spatial and Temporal Distribution of Rodents during the Epizootic and Enzootic Periods of Plague, with a Focus on Exu, Northeastern Brazil.

The plague caused by the Yersinia pestis bacterium is primarily a flea-transmitted zoonosis of rodents that can also be conveyed to humans and other mammals. In this work, we analyzed the spatial and temporal distribution of rodent populations during epizootic and enzootic periods of the plague in the municipality of Exu, northeastern Brazil. The geospatial analyses showed that all the rodent species appeared through the whole territory of the municipality, with different occurrence hotspots for the different species. Important fluctuations in the rodent populations were observed, with a reduction in the wild rodent fauna following the end of a plague epizootic period, mostly represented by Necromys lasiurus and an increase in the commensal species Rattus rattus. A higher abundance of rats might lead to an increased exposure of human populations, favoring spillovers of plague and other rodent-borne diseases. Our analysis highlights the role of wild rodent species as amplifier hosts and of commensal rats (R. rattus) as preserver hosts in the enzootic period of a specific transmission infection area.

First report of the L1014F kdr mutation in wild populations of Anopheles arabiensis in Cabo Verde, West Africa.

BACKGROUND: Due to the lack of vaccines, malaria control mainly involves the control of anopheline vectors (Anopheles spp.) using chemical insecticides. However, the prolonged and indiscriminate use of these compounds has led to the emergence of resistance in Anopheles populations in Africa. Insecticide resistance surveillance programs are less frequent in Cabo Verde than in other African countries. This study aimed to investigate the circulation of the L1014F and L1014S alleles in natural populations of Anopheles arabiensis collected from two sampling sites in the city of Praia, Cabo Verde. METHODS: Anopheles larvae were collected from the two sampling sites and reared in the laboratory until the adult stage. Mosquitoes were first morphologically identified by classical taxonomy and then by molecular species identification using molecular markers. All Anopheles arabiensis were subjected to PCR analysis to screen for mutations associated to resistance in the Nav gene. RESULTS: A total of 105 mosquitoes, all belonging to the Anopheles gambiae complex, were identified by classical taxonomy as well as by molecular taxonomy. Molecular identification showed that 100% of the An. gambiae senso lato specimens analyzed corresponded to An. arabiensis. Analysis of the Nav gene revealed the presence of L1014S and L1014F alleles with frequencies of 0.10 and 0.19, respectively. CONCLUSIONS: Our data demonstrated, for the first time, the presence of the L1014F allele in the An. arabiensis population from Cabo Verde, as well as an increase in the frequency of the kdr L1014S allele reported in a previous study. The results of this study demonstrate the need to establish new approaches in vector control programs in Cabo Verde.

A field survey using LAMP assay for detection of Schistosoma mansoni in a low-transmission area of schistosomiasis in Umbuzeiro, Brazil: Assessment in human and snail samples.

BACKGROUND: In Brazil, schistosomiasis is a parasitic disease of public health relevance, mainly in poor areas where Schistosoma mansoni is the only human species encountered and Biomphalaria straminea is one of the intermediate host snails. A nested-PCR based on a specific mitochondrial S. mansoni minisatellite DNA region has been successfully developed and applied as a reference method in Brazil for S. mansoni detection, mainly in host snails for epidemiological studies. The amplification efficiency of LAMP is known to be higher than PCR. The present work aimed to assess the utility of our previously described SmMIT-LAMP assay for S. mansoni detection in human stool and snail samples in a low-transmission area of schistosomiasis in the municipality of Umbuzeiro, Paraíba State, Northeast Region of Brazil. METHODOLOGY/PRINCIPAL FINDINGS: A total of 427 human stool samples were collected during June-July 2016 in the municipality of Umbuzeiro and an overall prevalence of 3.04% (13/427) resulted positive by duplicate Kato-Katz thick smear. A total of 1,175 snails identified as Biomphalaria straminea were collected from 14 breeding sites along the Paraíba riverbank and distributed in 46 pools. DNA from human stool samples and pooled snails was extracted using the phenol/chloroform method. When performing the SmMIT-LAMP assay a total of 49/162 (30.24%) stool samples resulted positive, including 12/13 (92.31%) that were Kato-Katz positive and 37/149 (24.83%) previously Kato-Katz negative. By nested-PCR, only 1/46 pooled DNA snail samples was positive. By SmMIT-LAMP assay, the same sample also resulted positive and an additional one was positive from a different breeding site. Data of human and snail surveys were used to build risk maps of schistosomiasis incidence using kernel density analysis. CONCLUSIONS/SIGNIFICANCE: This is the first study in which a LAMP assay was evaluated in both human stool and snail samples from a low-transmission schistosomiasis-endemic area. Our SmMIT-LAMP proved to be much more efficient in detection of S. mansoni in comparison to the 'gold standard' Kato-Katz method in human stool samples and the reference molecular nested-PCR in snails. The SmMIT-LAMP has demonstrated to be a useful molecular tool to identify potential foci of transmission in order to build risk maps of schistosomiasis.

Morbidity of mansoni schistosomiasis in Pernambuco-Brazil: Analysis on the temporal evolution of deaths, hospital admissions and severe clinical forms (1999-2014).

BACKGROUND: Current scientific information reported that due to successive treatments of schistosomiasis cases in endemic areas of Brazil in the last 30 years, there has been a decrease in severe clinical form (hepatosplenic) and mortality from upper gastrointestinal bleeding due to this disease. Against this information, literature data show that the state of Pernambuco presents significant percentage of deaths and hospitalizations due to schistosomiasis, and occurrence of severe clinical forms as schistosomiasis myeloradiculopathy and persistence of localities with high parasite loads. This scenario justified this research which seeking to update the morbidity and mortality of schistosomiasis in Pernambuco. OBJECTIVE: To conduct a temporal analysis on the evolution of deaths, hospital admissions and severe forms of Manson's schistosomiasis over the last 16 years in Pernambuco, Brazil. METHODS: It was performed a gathering secondary data on schistosomiasis, from healthcare information systems and from the records of Hospital das Clínicas, Federal University of Pernambuco (HC-UFPE), covering the period from 1999 to 2014. RESULTS: From 1999 to 2013 were registred 2578 deaths due to schistosomiasis and between 2008 and 2014 were recorded 473 hospitalizations for this disease. Among 1999-2014 were identified 1943 cases of schistosomiasis treated at the Hospital das Clínicas of Pernambuco. Among these cases, 72.6% (n. 1411) of the individuals presented the hepatosplenic clinical form (HE), 60.8% (n. 858) were at the age group 30-59 years (adults) and 58% were female. Among the HE cases, 4.6% (n. 58) had ascites, 43.2% (n. 556) had upper gastrointestinal bleeding and 39.1% (n. 489) had collateral circulation. The pattern of fibrosis in the liver E/EC (advanced fibrosis) and F/FC (very advanced fibrosis) occurred in 65.5% (n. 793) of cases. Between 1999-2014 the evolution curve of severe clinical forms of schistosomiasis remained stable, showing a tendency to decline from 2012. CONCLUSION: When compared to other states of Brazil, Pernambuco shows high numbers of deaths and hospital admissions due to schistosomiasis. The actions of the Schistosomiasis Control Program (PCE) have been developed in a disintegrated, disjointed and discontinuous way, which may explain the magnitude of deaths, hospitalizations and severe forms of the disease in Pernambuco, showing a lack of control and the maintenance of severe frame morbidity of schistosomiasis in this state.

Schistosomiasis transmission and environmental change: a spatio-temporal analysis in Porto de Galinhas, Pernambuco--Brazil.

BACKGROUND: In Brazil, schistosomiasis mansoni infection is an endemic disease that mainly affects the country's rural populations who carry out domestic and social activities in rivers and water accumulations that provide shelter for the snails of the disease. The process of rural migration to urban centers and the disorderly occupation of natural environments by these populations from endemic areas have favored expansion of schistosomiasis to locations that had been considered to be disease-free. Based on environmental changes that have occurred in consequent to an occupation and urbanization process in the locality of Porto de Galinhas, the present study sought to identify the relationship between those chances, measure by remote-sensing techniques, and establish a new endemic area for schistosomiasis on the coast of Pernambuco State--Brazil. METHODS: To gather prevalence data, two parasitological census surveys were conducted (2000 and 2010) using the Kato-Katz technique. Two malacological surveys were also conducted in the same years in order to define the density and infection rate of the intermediate host. Based on these data, spatial analyses were done, resulting in maps of the risk of disease transmission. To ascertain the environmental changes that have occurred at the locality, images from the QuickBird satellite were analyzed, thus resulting in land use maps. RESULTS: Over this 10-year period, the foci of schistosomiasis became more concentrated in the Salinas district. This area was considered to be at the greatest risk of schistosomiasis transmission and had the highest prevalence rates over this period. The study illustrated that this was the area most affected by the environmental changes resulting from the disorderly urbanization process, which gave rise to unsanitary environments that favored the establishment and maintenance of foci of schistosomiasis transmission, thereby consolidating the process of expansion and endemization of this parasitosis.