The Mearim River Watershed has multiple uses e.g. leisure, navigation, fishing and subsistence agriculture and constitutes the main source of supply for the populations of municipalities situated along its course. In addition to being a water supply source, the existence of the ‘pororoca’ (tidal bore) effect in a stretch of the lower course of the Mearim River attracts people from several Brazilian states and different countries, as it offers excellent conditions for surfing in fresh water. In this respect, given the importance of the watershed, this study was developed to report the detection of diarrheagenic Escherichia coli pathotypes in a stretch of the lower course of the Mearim River, located in the state of Maranhão, Brazil. Thirty water samples were collected from 10 sampling points. To quantify E. coli, the chromogenic enzymatic system was used and positive samples were isolated and biochemically identified. Pure cultures underwent DNA extraction by heating followed by polymerase chain reaction (PCR) characterization. At the time of the collections, an observation schedule was used to record information on the existence of rearing of livestock and domestic animals; businesses; residences; and fruit and vegetable farming on the riverbanks. The samples were analyzed for the mean populations of E. coli, which ranged from 444 to 2,585 MPN mL-1. Twenty bacterial isolates were identified and the diarrheal pathotypes ETEC, typical EPEC and atypical EPEC were detected. The detection of these pathotypes can represent an epidemiological risk and compromise several uses of this water resource, such as irrigation of fruits and vegetables consumed raw, fishing, animal watering and recreation. Structural investments in basic sanitation are essential to minimize environmental degradation resulting from anthropic activities and to act preventively in public health. In addition, the recovery of riparian forests along the watershed and the maintenance of vegetation in these areas are measures to reduce the transport of particles from the soil to the watercourses, improving the qualitative and quantitative characteristics of this water resource.

The aim of study is to feature the microbiological quality of two neotropical fish species from the quilombola area of Maranhão State, Brazil. In order to do so, 21 samples of Hoplerythrinus unitaeniatus and 21 samples of Cichlasoma bimaculatum were captured in flooded environment. Collected fish were euthanized in laboratory environment; muscle fragments were removed for microbiological analyses focused on enumerating molds and yeasts, viable strict and facultative mesophilic microorganisms and coagulase-positive staphylococci; on counting total and thermotolerant coliforms; and on investigating Escherichia coli and Salmonella sp. Microbiological results were compared to the Brazilian legislation, which establishes the list of microbiological standards for food products. Among the assessed fish, 9.52% were classified as non-acceptable for human consumption, based on the Salmonella parameter. Enumerated coagulase-positive staphylococci ranged from < 10 to 3.9 x 104 CFU/g; 9.52% of assessed fish were classified as having intermediate standard for human consumption, whereas 4.76% were classified as non-acceptable for such a purpose. E. coli counting ranged from 3.6 to > 1,100MPN/g; 4.76% of assessed fish were classified as having intermediate standard for human consumption, whereas 4.76% were classified as non-acceptable for such a purpose. Total and thermotolerant coliforms’ counting and the enumeration of viable strict and facultative aerobic microorganisms, as well as of molds and yeasts, have evidenced high microbial population rates; this finding suggests poor hygienic conditions at capture site, contaminated raw material and risk of incidence of enteropathogens. This finding has evidenced imbalance in the investigated environment, as well as compromised aquatic biodiversity.

The current study aimed to investigate the ectoparasitic diversity and gill alterations in Hoplerythrinus unitaeniatus (Characiformes: Erythrinidae) and Cichlasoma bimaculatum (Perciformes: Cichlidae) and evaluate the microbiological and physicochemical quality of water samples deriving from a Quilombola zone in Maranhão State, Brazil. Water samples and 42 fish specimens, 21 H. unitaeniatus and 21 C. bimaculatum, were collected from a floodable environment. Water samples were subjected to physicochemical and microbiological analyses in the laboratory environment. Fish specimens were euthanized to collect and identify ectoparasites in animals' mucus, body surface, and gills, as well as to enable the histological analysis of the second right gill arch. The herein-identified ectoparasites have shown 30.95% prevalence and comprised three phyla: Platyhelminthes, Trematoda and Arthropoda. The herein-identified main histological changes comprised incomplete and complete fusion of several lamellae, lifting of respiratory epithelium, lamellar disorganization, lamellar epithelial hyperplasia, and blood sinus dilation. The herein calculated histological alteration index has shown that 23.80% of specimens presented mild-to-moderate tissue damage, 4.77% presented moderate-to-severe tissue changes, and 9.52% presented irreparable tissue damage. It was possible concluding that histological gill lesions identified in fish specimens analyzed may be adaptive responses to the affected environment and the incidence of ectoparasites.