Mosquito-transmitted viruses - the great Brazilian challenge

ABSTRACT Arboviruses pose a serious threat to public health worldwide, overloading the healthcare system and causing economic losses. These viruses form a very diverse group, and in Brazil, arboviruses belonging to the families Flaviviridae and Togaviridae are predominant. Unfortunately, the number of arboviruses increases in proportion with factors such as deforestation, poor sanitation, climate changes, and introduction of new viruses like Chikungunya virus and Zika virus. In Brazil, dengue is endemic, along with the presence of other arboviruses. The situation is complicated by the scarcity of diagnostic infrastructure and the absence of approved vaccines for these diseases. Disease control, thus, relies solely on vector control. Therefore, enhanced clinical knowledge and improved general awareness about these arboviruses are indispensable to tackle diagnostic inadequacies.

Fiebre de Chikungunya: enfermedad infrecuente como emergencia médica en Cuba / Chikungunya fever: uncommon disease as a medical emergency in Cuba

Debido a la emergencia en el Caribe por fiebre de Chikungunya, y teniendo en cuenta que no tiene antecedentes en Cuba, además de la situación entomológica que presenta la provincia de Santiago de Cuba, donde existen vectores transmisores de enfermedades, tales como mosquitos Aedes aegypti y Aedes albopictus; se realizó una revisión bibliográfica exhaustiva, para contribuir a la actualización sobre el tema de toda la comunidad médica de la provincia.

Due to the emergency in the Caribbean caused by Chikungunya fever, and keeping in mind that it has no history in Cuba, besides the entomological situation that presents Santiago de Cuba province, where vectors transmitting diseases exist, such as Aedes aegypti and Aedes albopictus mosquitoes, an exhaustive literature review was carried out, to contribute to the updating on the topic of the whole medical community from the province.

Preparação e resposta à introdução do vírus Chikungunya no Brasil / Preparation and response to introduction of Chikungunya virus in Brazil / Preparación y respuesta a la introducción del virus Chikungunya en Brasil

O CHIKV é um vírus RNA que pertence ao gênero Alphavírus da família Togaviridae. O nome chikungunya deriva de uma palavra em Makonde que significa aproximadamente “aqueles que se dobram”, descrevendo a aparência encurvada de pacientes que sofrem de artralgia intensa. Casos humanos com febre, exantema e artrite aparentando ser CHIKV foram relatados no início de 1770. Porém, o vírus não foi isolado do soro humano ou de mosquitos até a epidemia na Tanzânia de 1952-53. Outros surtos ocorreram subsequentemente na África e na Ásia. Muitos ocorreram em pequenas comunidades ou comunidades rurais. No entanto,na Ásia, cepas de CHIKV foram isoladas durante grandes surtos urbanos em Bangkok eTailândia em 1960 e em Calcutá e Vellore, na Índia, durante as décadas de 60 e 70.

Entomological study of chikungunya infections in the State of Kelantan, Malaysia.

Background & objectives: Chikungunya infection has become a public health threat in Malaysia since the 2008 nationwide outbreaks. Aedes albopictus Skuse has been identified as the chikungunya vector in Johor State during the outbreaks. In 2009, several outbreaks had been reported in the State of Kelantan. Entomological studies were conducted in Kelantan in four districts, namely Jeli, Tumpat, Pasir Mas and Tanah Merah to identify the vector responsible for the virus transmission. Methods: CHIKV cases records were obtained from State Health Department, Kelantan and localities involved were identified. Larva survey was conducted to collect the immature mosquito stages. Modified aspirators were used to collect the adult mosquitoes. All samples on dry ice were transferred to laboratory and the presence of the virus was detected using reverse transcriptase PCR. Results: A total of 1,245 mosquito larvae were collected during larval survey and 2,019 adult mosquitoes were collected using aspirator. From these collections, 640 mosquito pools were tested for the presence of CHIKV by RT-PCR but none found positive. Ae. albopictus was the most abundant mosquito collected, followed by Culex sp., Armigeres sp. and Anopheles sp. A total of 2, 814 artificial containers were inspected during the study. Interpretation & conclusions: Since none of the mosquito samples was found to be positive for chikungunya virus, the vector(s) of chikungunya virus in these localities could not be identified.

Rapid spread of Chikungunya virus infection in Orissa: India.

Background & objectives : A large number of cases of undiagnosed fever and joint pain were reported from different parts of the State of Orissa since February 2006. Epidemiological and laboratory investigation were carried out to confirm the cause of emerging illness, which was provisionally suspected as Chikungunya (CHIK) fever. Methods: Upon getting the reports of suspected CHIK like illness in different parts of the State, epidemic investigations were carried out in the outbreak affected villages. Case history was recorded, clinical examination undertaken and blood samples collected for seroconfirmation for CHIK IgM antibody using ELISA based kit. Simultaneously vector survey was also carried out. Results: With no previous record of CHIK infection in the State, the first outbreak was confirmed during February 2006. Subsequently, the infection spread to 13 of 30 districts in different episodes covering 79 villages till November 2007. Attack rate was 9-43 per cent in the different outbreaks with average seropositivity of 24 per cent to CHIK specific IgM. Morbidity was high though no deaths were recorded. Aedes aegypti and Ae. albopictus were identified as the possible vectors for transmission. Interpretation & conclusions : The report confirmed emergence of CHIK infection in the State of Orissa, India, and its spread to a larger geographic zone in a short period which warrants public health measures to control further spread.

Preparación y respuesta ante la eventual introducción del virus chikungunya en las Américas / Preparation and response to the eventual introduction of the virus Chikungunya in the Americas

Las siguientes guías fueron concebidas para ser adaptadas por cada País Miembro para mejorar los conocimientos sobre esta amenaza y para brindar las herramientas necesarias que permitan establecer las estrategias más adecuada para prevenir la importación de CHIKV a la Región, o para su control. Proporcionan orientación sobre cómo detectar un brote de la enfermedad, desarrollar las investigaciones epidemiológicas y prevenir o mitigar la diseminación de la enfermedad en la Región. Alentamos a las personas involucradas en la aplicación de estas guías a tener en cuenta todos los conocimientos disponibles y la capacidad propia de cada país para afrontar la eventual introducción del CHIKV. Se deben tomar medidas cuanto antes para poner en marcha las acciones necesarias para disminuir el impacto que este nuevo arbovirus que puede existir en nuestra Región.

Amenaza del virus Chikungunya: la globalización de las enfermedades transmitidas por insecto vector / The Chikungunya threat: the globalization of vectorborne diseases

El brote de infección Chikungunya (CHIKV) que se produjo en el verano de 2007 en una zona templada del norte de Italia, constituye un nuevo modelo para la difusión de una enfermedad tropical fuera de los lugares convencionales, esta situación ha sido causada principalmente, por la peligrosa mezcla de la gran población de un competente vector, el mosquito tigre de Asia, y la posibilidad de que una persona regrese de la zona de la difusión normal de CHIKV durante la fase de viremia asintomática. Teniendo en cuenta las dificultades para controlar la propagación de Aedes albopictus y el gran número de personas que viajan hacia y desde los ámbitos de la difusión normal de las enfermedades transmitidas por vectores tropicales, pensamos que la epidemia de 2007 podría ser sólo la primera de una serie de posibles brotes. En conclusión, esta epidemia urbana de la infección CHIKV en un país templado, determina una nueva perspectiva en la preparación para las inesperadas infecciones emergentes por el virus, las que deben ser afrontadas mediante una estrategia combinada de difusión de vigilancia de vectores, y el diagnóstico inmediato de cualquier caso sospechoso de importación transmitido por vectores de enfermedades exóticas.

The outbreak of CHIKV infection that occurred in summer 2007 in a temperate area of northern Italy constitues a new model for the diffusion of a tropical disease outside the conventional locations; this situation has been caused mainly by the dangerous mixture of the large population of a highly competent vector, the Asian tiger mosquito, and the possibility that an individual comes back from the area of normal diffusion of CHIKV during the asymptomatic viremic stage. Considering the difficulties in controlling the spread of Aedes albopictus and the large number of people travelling to and from the areas of normal diffusion of vector-borne tropical diseases, we think that the 2007 epidemic could be only the first of a possible series of these aoutbreaks. In conclusion, this urban epidemic of CHIKV infection in a temperate country determines a new perspective in the preparedness to unexpected emerging virus infections that must be faced by using a combined strategy of vector diffusion monitoring and immediate diagnosis of any suspected cases of imported vector-borne exotic disease.

Failure to demonstrate experimental vertical transmission of the epidemic strain of Chikungunya virus in Aedes albopictus from La Réunion Island, Indian Ocean

Aedes albopictus was responsible for transmission in the first outbreak of chikungunya (CHIK) on La Réunion Island, Indian Ocean, in 2005-2006. The magnitude of the outbreak on this island, which had been free of arboviral diseases for over 30 years, as well as the efficiency of Ae. albopictus as the main vector, raises questions about the maintenance of the CHIK virus (CHIKV) through vertical transmission mechanisms. Few specimens collected from the field as larvae were found to be infected. In this study, Ae. albopictus originating from La Réunion were orally infected with a blood-meal containing 10(8) pfu/mL of the CHIKV epidemic strain (CHIKV 06.21). Eggs from the first and second gonotrophic cycles were collected and raised to the adult stage. The infectious status of the progeny was checked (i) by immunofluorescence on head squashes of individual mosquitoes to detect the presence of viral particles or (ii) by quantitative RT-PCR on mosquito pools to detect viral RNA. We analysed a total of 1,675 specimens from the first gonotrophic cycle and 1,709 from the second gonotrophic cycle without detecting any viral particles or viral RNA. These laboratory results are compared to field records.

Community-centred approach for the control of Aedes spp. in a peri-urban zone in the Andaman and Nicobar Islands using temephos.

Background. Chikungunya fever struck the Andaman and Nicobar Islands in July 2006. From the entomological point of view, dengue and chikungunya are hard to control due to the high prevalence of Aedes aegypti in both urban and rural areas. Mobilizing communities for the control of Aedes aegypti has not been attempted in India. Methods. We did a prospective observational feasibility study in one peri-urban locality (Brookshabad) to assess the Aedes spp. infestation and subsequently test the efficacy of a community-based approach to control Aedes aegypti. An Aedes infestation larval survey was done with the assistance of community volunteers using the single larval survey (SLS) technique. House index, container index and Breteau index reflecting the relative prevalence and infestation levels were estimated. Various information, education and communication (IEC) campaign tools were developed to disseminate information about the prevalent situation. Several talks were organized to sensitize and motivate the people to realize the problem and participate in solving it. A two-pronged strategy, viz. environmental management through source reduction and anti-larval campaign using temephos was adopted to combat Aedes infestation through community involvement. Results. A total of 533 water-holding containers were searched for Aedes larvae, both indoors (188/533, 35.3%) and outdoors (345/533, 64.7%) from 104 (104/235, 44.3%) premises. Of these, 109 containers (95% CI 17.19%–24.03%) were found to support Aedes spp. larval breeding (20.45%). The Breteau index was 104.8%. Aedes aegypti predominated followed by Aedes albopictus. The most abundant water-holding containers supporting Aedes breeding were plastic, metal drums and cement tanks. These waterholding containers were targeted for temephos application by the community volunteers. Forty rounds of temephos applications were carried out during the study period. The number of containers supporting Aedes aegypti breeding reduced significantly within 1 month post-intervention by community volunteers. As a result the Breteau and house indices dropped from 104.8% to 2.7% and 44.23% to 2.6%, respectively. Thereafter, the indices remained at zero level till completion of the study. Conclusion. Larval indices indicate that Aedes aegypti is well established in peri-urban Brookshabad. Predominance of this mosquito species indicates infiltration into the peri-urban locality and beginning of displacement of Aedes albopictus. Epidemiologically, 3 categories of water-holding containers, viz. plastic, metal drums and cement tanks facilitate breeding of Aedes aegypti. Consequently, targeted source reduction as one way of selectively attacking the most important types of containers with temephos is feasible. Community involvement and networking with the residents allowed for a communitycentred approach to combat Aedes aegypti infestation. As an outcome of this approach, the larval indices reduced significantly and remained low. We suggest that a control strategy emphasizing the use of temephos through a community-centred approach should be considered for these islands. However, close monitoring of this approach is warranted for long term sustainability

Entomo-epidemiological investigations on chikungunya outbreak in the Lakshadweep islands, Indian Ocean.

Background & objectives: An outbreak of chikungunya fever characterized by prolonged incapacitation in the Lakshadweep islands in Indian Ocean occurred in November 2006. We undertook the entomological and epidemiological investigations on the Chikungunya outbreak in the Lakshadweep islands, Indian Ocean. Methods: Epidemic information in the affected places was obtained from the local hospital records. Entomological observations like larval survey and the adult resting/landing collections by the hand collection methods were individually conducted in the two affected islands Andrott and Kalpeni in November and December 2006. Results: The main breeding sources of the mosquitoes were the rodent-devoured coconuts, coconut shells, areca nut soaking mud and plastic pots, discarded containers, grinding stones, metal containers and plastic containers. Aedes albopictus was pre-dominantly present in the Lakshadweep islands. Interpretation & conclusion: It is concluded that the routine campaigns need to be organized regularly within the community highlighting the potential breeding grounds of mosquitoes and the possible control methods. Source reduction strategies like destruction of coconut shells and rodent-devoured coconuts by burning or by burying them inside the ground. Ae. albopictus played major role as the vector mosquitoes responsible for the chikungunya transmission.

A study on chikungunya outbreak during 2007 in Kerala, south India.

Background & objectives: The first chikungunya outbreak occurred in Kerala during 2006 affecting 14 districts, followed by another during May 2007 affecting almost whole of the State. Four of the worst affected districts viz, Pathanamthitta, Idukki, Kottayam and Thrissur were surveyed during 2007 to understand the magnitude of the problem of chikungunya fever, particularly clinical signs and symptoms. Methods: A total of 1265 persons from 310 houses were surveyed door-to-door in 20 different localities representing four affected districts. The history and examination findings from 354 clinically diagnosed chikungunya cases were recorded. The symptoms recorded were fever, headache, myalgia, arthralgia, itch/rash, oedema, eye congestion, eye pain, oral ulcers, distaste, nausea, vomiting and haemorrhage. Results: The major symptoms were fever (100%), headache (97.5%), arthralgia (99.4%) and myalgia (99.4%). A significant difference was observed in oedema, distaste, nausea and headache among different age groups and these symptoms were reported to be lower (12.2-89.8%) in younger age group than in older age group (90.4-100%). No genderwise difference was observed for any of the symptoms. In clinically diagnosed chikungunya cases higher age group (>35 years) found with higher rate of severity with symptoms of oedema, distaste, nausea and headache when compared with lower age group (1-35 yr). Interpretation & conclusions: Chikungunya invaded Kerala State for the first time in 2006 and continues to be a major vector borne disease in the State. The clinical symptoms in affected cases highlighted high fever, sever myalgia and prolonged arthralgia, with occasional history of skin itch/rash (petechiae).