Occurrence of the Sylvatic Yellow Fever Vector Mosquito Haemagogus leucocelaenus (Diptera: Culicidae) in an Atlantic Forest Fragment of the Touristic State of Rio de Janeiro, Brazil

The yellow fever virus is estimated to cause 30,000 deaths each year worldwide, with the majority of cases and deaths occurring in Africa. The virus is also endemic to Central and South America, including northern and western Brazil. The sylvatic cycle of the virus is related to wild and rural areas, with nonhuman primates as the primary host and wild mosquitoes, specifically from the genera Haemagogus, as vectors. The diversity of the mosquito community plays a significant role in the increase of pathogen transmission to humans. In the present study, we detected fluctuation in populations of vector mosquitoes using ovitraps for Culicidae egg collection. The study area is a forest fragment of the Atlantic Forest, one of the most threatened biomes in Brazil. This biome has been suffering significant deforestation due to anthropic activity. Worryingly, the proximity of human populations to forest environments increases the risk of spreading disease from forest fragments to urban areas. Our findings showed that the highest egg abundance occurred in December 2019, with a significant difference (p = 0.005) between rainy and dry seasons. Most eggs were collected during the rainy period. Subsequent quantification of specimens from epidemiologically relevant species hatched from field-collected eggs resulted in 1,131 (86%) Haemagogus leucocelaenus (Dyar & Shannon, 1924), 111 (8%) Aedes terrens (Walker, 1856), 47 (4%) Aedes albopictus (Skuse, 1894), and 21 (2%) Haemagogus janthinomys (Dyar, 1921). Finally, we assessed the behavior of different vector species performing oviposition on the same breeding site. The highest correlation coefficient was observed between Ae. albopictus and Ae. terrens (rho = 0.52) concerning other Culicidae species. Therefore, we believe that Culicidae population surveillance is crucial for disease monitoring since the increase in specimens of a number of vector species influences the emergence of yellow fever cases in nonhuman primates and human populations.

Interaction of Haemagogus leucocelaenus (Diptera: Culicidae) and Other Mosquito Vectors in a Forested Area, Rio de Janeiro, Brazil

The yellow fever (YF) virus has been detected throughout Brazil, with the occurrence of human cases, cyclic epizootics, and its isolation from Haemagogus janthinomys and Hg. leucocelaenus. We assessed the seasonal occurrence, egg abundancy, and oviposition interaction of mosquito vector species captured at a Private Natural Heritage Reserve in the Atlantic Forest biome. A total of 2943 eggs and 1538 mosquito larvae were collected from which 1231 belonged to entomologically important species. Ovitraps were used to collect immature mosquitoes from September 2019 to January 2021. The Mann–Whitney test was used to assess the differences in the abundance of eggs between rainy and dry seasons. Kruskal–Wallis and Dunn’s post hoc tests were used to evaluate the significance of the differences in the number of individuals from vector species. The highest percentage of mosquito vector eggs were collected during the rainy season, from December to February. Most eggs recovered from ovitraps belonged to the species Hg. leucocelaenus, representing 85% of all mosquito eggs identified. The other species had lower abundances and percentages: Aedes terrens (7%), Haemagogus janthinomys (5%) and Aedes albopictus (3%). The species that shared breeding sites with a higher frequency were Hg. leucocelaenus and Hg. janthinomys, with a statistically positive correlation (ρ = 0.74). This finding suggests that maybe the presence of Hg. leucocelaenus eggs acted as an attractant for Hg. janthinomys or vice versa. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control approaches directed against specific pathogen vectors of medical and veterinary importance.

Oviposition activity of Haemagogus leucocelaenus (Diptera: Culicidae) during the rainy and dry seasons, in areas with yellow fever virus circulation in the Atlantic Forest, Rio de Janeiro, Brazil

The present study aims to analyze the effectiveness of ovitraps in the capture of Hg leucocelaenus eggs and evaluate the influence of the dry and rainy seasons on their abundance and hatching rates. The eggs were collected in the Atlantic Forest of State of Rio de Janeiro, Brazil, an area in which the yellow fever virus is known to circulate. We distributed 15 ovitraps in three sampling points, with five ovitraps per point. We distributed 15 ovitraps in three sampling points on trees within a forested area, which were sequentially numbered, monitored, and replaced every two weeks from October 2016 to April 2018. There was a high dominance of Hg. leucocelaenus eggs (98.4%) and a variation in egg hatching rates between the wet and dry seasons. These rates were 1.5 times higher in the rainy season than in the dry season. The rainy season also showed a greater abundance of eggs and higher values of ovitrap positivity and egg density indexes in the installed ovitraps. The abundances of Hg. leucocelaenus eggs were positively correlated with mean monthly temperature and air humidity but not significantly correlated with accumulated precipitation. These results, as well as their implications for the possible use of ovitraps to monitor vector mosquitoes of yellow fever in the study region, are discussed.

Bionomy of Mosquitoes in Bamboo Internodes in an Atlantic Forest Remnant of the State of Rio De Janeiro, Brazil

Living bamboo stalks are one of the most specialized habitats for mosquito oviposition and immature development. Most of the mosquito species that breed in these habitats are sylvatic, and some are of importance for public health as possible vectors of pathogens. Perforated internodes are a very specialized environment due to the difficulty of access. Furthermore, due to their relatively simple fauna, they represent a valuable model for ecological studies that may be applicable to more complex environments. This study aims to assess the mosquito bionomics of species raised in bamboo internodes. Therefore, the diversity of mosquito species and the influence of abiotic variables (pH and temperature) on the distribution of mosquitoes that breed in this habitat were analyzed. The study area is a fragment of Atlantic Forest within the Association of da Armada (ATA) in Nova Iguaçu, state of Rio de Janeiro, Brazil. Immature mosquitoes were sampled with suction tubes (mouth aspirators) between August 2017 and July 2018. A total of 3,170 larvae were collected in 5 bamboo plants, each with 8 stalks perforated. Of these, 688 larvae reached the adult stage, representing 10 genera and 19 species. The most common species were Culex neglectus (43%), Trichoprosopon digitatum (22%), Culex iridescens (8%), Sabethes identicus (7%), and Orthopodomyia albicosta (7%). The richness of the immatures collected in the ATA was 19 species, with a diversity of 1.10 and Shannon evenness of 0.57. A diverse composition of Culicidae in bamboo stalks was found, although dominance was low.

Comparative Analysis Between Sampling Methods for Immature Mosquitoes in an Atlantic Forest Fragment in Brazil

In this study, traps were set out to improve mosquito monitoring, study their viability, and determine the most suitable traps for female mosquito species of epidemiological importance during oviposition. The effectiveness of 3 types of traps (bamboo traps, tire traps, and ovitraps) were compared at 2 sampling sites. A total of 24 traps were installed on the ground at elevations of 3 m, 6 m, and 9 m in a fragment of the Atlantic Forest in the municipality of Nova Iguaçu, Rio de Janeiro State, Brazil. The samplings took place every 2 wk from July 2017 to June 2018. A total of 1,854 mosquitoes belonging to 16 different species were identified, of which 2 species are involved in the transmission of arbovirus: Haemagogus leucocelaenus (Dyar and Shannon) and Aedes albopictus Skuse. Larval tire traps were the most effective at trapping females laying eggs, followed by ovitraps. The results were consistent with the usual habitats of certain species that were found in tire traps, which are artificial objects commonly found in human environments.

Seasonal population dynamics of the primary yellow fever vector Haemagogus leucocelaenus (Dyar & Shannon) (Diptera: Culicidae) is mainly influenced by temperature in the Atlantic Forest, southeast Brazil

BACKGROUND

Southeast Brazil has recently experienced a Yellow Fever virus (YFV) outbreak where the mosquito Haemagogus leucocelaenus was a primary vector. Climatic factors influence the abundance of mosquito vectors and arbovirus transmission.

OBJECTIVES

We aimed at describing the population dynamics of Hg. leucocelaenus in a county touched by the recent YFV outbreak.

METHODS

Fortnightly egg collections with ovitraps were performed from November 2012 to February 2017 in a forest in Nova Iguaçu, Rio de Janeiro, Brazil. The effects of mean temperature and rainfall on the Hg. leucocelaenus population dynamics were explored.

FINDINGS

Hg. leucocelaenus eggs were continuously collected throughout the study, with a peak in the warmer months (December-March). The climatic variables had a time-lagged effect and four weeks before sampling was the best predictor for the positivity of ovitraps and total number of eggs collected. The probability of finding > 50% positive ovitraps increased when the mean temperature was above 24ºC. The number of Hg. leucocelaenus eggs expressively increase when the mean temperature and accumulated precipitation surpassed 27ºC and 100 mm, respectively, although the effect of rainfall was less pronounced.

MAIN CONCLUSIONS

Monitoring population dynamics of Hg. leucocelaenus and climatic factors in YFV risk areas, especially mean temperature, may assist in developing climate-based surveillance procedures to timely strengthening prophylaxis and control.

Dispersal of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in an urban endemic dengue area in the State of Rio de Janeiro, Brazil

Experimental releases of female Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus were performed in August and September 1999, in an urban area of Nova Igua u, State of Rio de Janeiro, Brazil, to estimate their flight range in a circular area of 1,600 m where 1,472 ovitraps were set. Releases of 3,055 Ae. aegypti and 2,225 Ae. albopictus females, fed with rubidium (Rb)-marked blood and surgically prevented from subsequent blood-feeding, were separated by 11 days. Rb was detected in ovitrap-collected eggs by atomic emission spectrophotometry. Rb-marked eggs of both species were detected up to 800 m from the release point. Eggs of Ae. albopictus were more numerous and more heterogeneously distributed in the area than those of Ae. aegypti. Eggs positively marked for Rb were found at all borders of the study area, suggesting that egg laying also occurred beyond these limits. Results from this study suggest that females can fly at least 800 m in 6 days and, if infected, potentially spread virus rapidly.

Epilepsy surgery without invasive EEG. Early results of a new program

A total of 42 patients were submitted to a clinical, behavioural and neuropsychological evaluation with the objective of eventual surgical treatment of epilepsy refractory to the usual clinical therapies. Prolonged video-EEG monitoring, MRI hippocampal volume measurement, lateralization of speech and memory using the amobarbital (Wada) test were used. Of 18 operated cases, 12 were submitted to temporal lobectomy, with a follow-up of 6-30 months; 8 patients had significant improvement in seizures control; 2 patients had partial improvement in seizure frequency and intensity; 2 patients had no improvement in seizure control. One patient underwent right frontal lobectomy with total remission of seizures and 5 had callosotomy with varying degrees of success. There was no mortality. Morbidity included one subdural hematoma, one transient hemiparesis, one episode of mania, one lobar pneumonia and frequent immediately post-operative muscular tension headaches. These early results indicate good results of temporal lobectomy patients investigated through a non-invasive presurgical evaluation.

The intracarotid amobarbital procedure (Wada test) with two protocols combined, Montreal and Seattle

The intracarotid amobarbital procedure was carried out in 8 male and 7 female candidates to temporal lobectomy, and a female candidate to frontal lesionectomy, aged 18-50 (mean 32.5) years. Language and memory were tested after injection in each hemisphere. Both were measured by the Montreal procedure. In 9 patients language and memory were evaluated with the Seattle procedure too. In 12 patients the left hemisphere was dominant for language; three had bilateral dominance. In 1 patient the Seattle procedure demonstrated the dominant hemisphere by relatively slowness of speech during the drug effect in the left hemisphere. Memory was defined to be in the left hemisphere in 12 patients, in the right in 2, bilateral in 1 and in another lateralization was not possible. In 1 patient memory dominance was determined by the Montreal protocol alone because of lack of cooperation. These early results indicate that the methods may be complementary for determination of language and memory dominance in epilepsy surgery candidates.

Carbamazepine kinetics in cardiac patients before and during amiodarone

Carbamazepine and amiodarone may often be used together, especially in countries where cardiomyopathies are common. In this study single doses of carbamazepine (400 mg) were given to patients with cardiac disease before and after one month of therapy with amiodarone, 400 mg daily. The kinetic profile of carbamazepine, its free fraction, and serum amiodarone, were measured at the two occasions. There was no statistically significant change in carbamazepine kinetics or free fraction, before and after the introduction of amiodarone. The concentrations of amiodarone after one month of therapy were low. It is suggested that the possible interaction in the hepatic metabolism was not demonstrated because amiodarone concentrations were not enough to inhibit carbamazepine metabolism.

[Loading-doses of carbamazepine and diphenylhydantoin: use in high-risk patients]

Loading-doses of phenytoin (1000 mg) and carbamazepine (600 mg) were given orally respectively to 10 and 6 patients with uncontrolled epileptic seizures secondary to acute neurological disorders or alcohol withdrawal. In the phenytoin group age varied between 12-73 years and serum concentrations at 2, 4, 6, 8, 12 and 18 hours after drug administration were 7.6, 8.8, 8.7, 8.7, 7.2 and 6.5 micrograms/ml (means). A quantitative method did not detect important side-effects. In the carbamazepine group age varied between 25-56 years and serum concentrations at the same times were 3.9, 5.3, 6.5, 7.5, 7.4 and 8.2 micrograms/ml. Side-effects were discrete. Further medication was not necessary in the 24 hours after drug administration. Although both regimens controlled the clinical situation without relevant side-effects serum concentrations were sub-therapeutic in the case of phenytoin. We suggest the ideal phenytoin oral loading-dose is 1500 mg. The carbamazepine load produced therapeutic concentrations. The stability of serum concentrations for the period of the study shows that those regimens are useful in the subacute control of epileptic seizures in the maintenance treatment of status epilepticus and in alcohol withdrawal.