Aedes albopictus has been known as efficient vector of dengue in Asian countries and its wide displacement of Ae. aegypti has been documented in many parts of the world. The present survey was carried out to update the distribution of Ae. albopictus in northeast Mexico and to report the first record of parasitism of mosquitoes by Ascogregarina taiwanensis in Mexico.
Human landing collections were conducted in the month of May every year between 2007 and 2009 across the three states, Nuevo Leon (NL), Tamaulipas and Coahuila in northeast Mexico. Six human bait collections were also organized at the cemetery of Gomez Farias (GF), a village in southern Tamaulipas during the rainy and dry seasons in 2010. Aedes albopictus caught in 2010 were dissected for parasitic protozoan gregarines.
The results of human landing collections carried out during 2007-10 across the three states of northeast zone of Mexico revealed that Ae. albopictus is invading along the route between Monterrey City in NL and Tampico, Tamaulipas, but not into the arid state of Coahuila. Aedes albopictus was recorded in nine new municipalities in addition to the 15 municipalities reported before 2005. Furthermore, six human-bait collections performed during the dry and rainy seasons in 2010 at the cemetery of GF suggest the exclusion of Ae. aegypti on that site. Dominance was shared by Ae. quadrivittatus, another container-inhabitant but indigenous species, and Ae. albopictus during the dry and rainy seasons, respectively. The results of dissection of the mosquitoes for gregarines revealed the parasitism of Ae. albopictus by A. taiwanensis.
The results of this study showed that Ae. albopictus has spread to all the municipalities in the northeastern Mexico except the arid area and reported the first record of parasitic protozoan A. taiwanensis in Mexico. We recommend further studies on larval and adult populations of natural container-occupant mosquitoes in northeastern Mexico in order to have a better documentation of the impact of Ae. albopictus upon the indigenous species community, and its epidemiological role in dengue transmission.
After more than a half century without recognized local dengue outbreaks in the continental United States, there were recent outbreaks of autochthonous dengue in the southern parts of Texas (2004-2005) and Florida (2009-2011). This dengue reemergence has provoked interest in the extent of the future threat posed by the yellow fever mosquito, Aedes (Stegomyia) aegypti (L.), the primary vector of dengue and yellow fever viruses in urban settings, to human health in the continental United States. Ae. aegypti is an intriguing example of a vector species that not only occurs in the southernmost portions of the eastern United States today but also is incriminated as the likely primary vector in historical outbreaks of yellow fever as far north as New York, Philadelphia, and Boston, from the 1690s to the 1820s. For vector species with geographic ranges limited, in part, by low temperature and cool range margins occurring in the southern part of the continental United States, as is currently the case for Ae. aegypti, it is tempting to speculate that climate warming may result in a northward range expansion (similar to that seen for Ixodes tick vectors of Lyme borreliosis spirochetes in Scandinavia and southern Canada in recent decades). Although there is no doubt that climate conditions directly impact many aspects of the life history of Ae. aegypti, this mosquito also is closely linked to the human environment and directly influenced by the availability of water-holding containers for oviposition and larval development. Competition with other container-inhabiting mosquito species, particularly Aedes (Stegomyia) albopictus (Skuse), also may impact the presence and local abundance of Ae. aegypti. Field-based studies that focus solely on the impact of weather or climate factors on the presence and abundance of Ae. aegypti, including assessments of the potential impact of climate warming on the mosquito's future range and abundance, do not consider the potential confounding effects of socioeconomic factors or biological competitors for establishment and proliferation of Ae. aegypti. The results of such studies therefore should not be assumed to apply in areas with different socioeconomic conditions or composition of container-inhabiting mosquito species. For example, results from field-based studies at the high altitude cool margins for Ae. aegypti in Mexico's central highlands or the Andes in South America cannot be assumed to be directly applicable to geographic areas in the United States with comparable climate conditions. Unfortunately, we have a very poor understanding of how climatic drivers interact with the human landscape and biological competitors to impact establishment and proliferation of Ae. aegypti at the cool margin of its range in the continental United States. A first step toward assessing the future threat this mosquito poses to human health in the continental United States is to design and conduct studies across strategic climatic and socioeconomic gradients in the United States (including the U.S.-Mexico border area) to determine the permissiveness of the coupled natural and human environment for Ae. aegypti at the present time. This approach will require experimental studies and field surveys that focus specifically on climate conditions relevant to the continental United States. These studies also must include assessments of how the human landscape, particularly the impact of availability of larval developmental sites and the permissiveness of homes for mosquito intrusion, and the presence of other container-inhabiting mosquitoes that may compete with Ae. aegypti for larval habitat affects the ability of Ae. aegypti to establish and proliferate. Until we are armed with such knowledge, it is not possible to meaningfully assess the potential for climate warming to impact the proliferation potential for Ae. aegypti in the United States outside of the geographic areas where the mosquito already is firmly established, and even less so for dengue virus transmission and dengue disease in humans.
The international trade in used tires, coupled with the ability to lay non-desiccating eggs, has enabled Aedes albopictus (Skuse) (Diptera: Culicidae) to travel and establish on new continents, including North, Central, and South America, the Caribbean, Australasia, Africa, and Europe. Concerns have been raised over its potential role in the transmission of arboviruses and Dirofilaria nematodes. Following importation into northerly latitudes, photoperiodically-induced egg diapause enables establishment of Ae. albopictus, and a number of abiotic factors determine the subsequent seasonal activity. The United Kingdom (U.K.) imports over 5 million used tires annually, and this seems the most likely route by which Ae. albopictus would be imported. The anthropophilic and container-breeding nature of Ae. albopictus could cause an urban human biting nuisance and the potential for involvement in (human and veterinary) disease transmission cycles needs to be assessed. This paper addresses the likelihood for importation of Ae. albopictus into the U.K. and assesses, using a Geographic Information Systems (GIS)-based model, the ability for Ae. albopictus to establish, and the likely seasonal activity. It also reviews its possible role as a potential disease vector in the U.K. The model predicts that abiotic risk factors would permit establishment of Ae. albopictus throughout large parts of lowland U.K., with at least four to five months of adult activity (May-September), being more prolonged in the urban centers around London and the southern coastal ports. Pre-emptive surveillance of possible imported Ae. albopictus, through a targeted approach, could prevent the establishment of this exotic mosquito and mitigate any subsequent human and animal health implications for the U.K., either now or in the future.
Francisella tularensis is the cause of the zoonotic disease tularemia. In Sweden and Scandinavia, epidemiological studies have implicated mosquitoes as a vector. Prior research has demonstrated the presence of Francisella DNA in infected mosquitoes but has not shown definitive transmission of tularemia from a mosquito to a mammalian host. We hypothesized that antimicrobial peptides, an important component of the innate immune system of higher organisms, may play a role in mosquito host-defense to Francisella. We established that Francisella sp. are susceptible to two cecropin antimicrobial peptides derived from the mosquito Aedes albopictus as well as Culex pipiens. We also demonstrated induced expression of Aedes albopictus antimicrobial peptide genes by Francisella infection C6/36 mosquito cell line. We demonstrate that mosquito antimicrobial peptides act against Francisella by disrupting the cellular membrane of the bacteria. Thus, it is possible that antimicrobial peptides may play a role in the inability of mosquitoes to establish an effective natural transmission of tularemia.
Most, if not all, people are sensitized to mosquito bites in childhood. Cutaneous symptoms include immediate wheal-and-flare reactions and delayed bite papules, which tend to be more severe at the onset of the mosquito season. Systemic reactions to mosquito bites are, however, very rare. Recent immunoblot studies have demonstrated IgE antibodies to Aedes communis mosquito saliva 22 and 36 kD proteins. This confirms that specific sensitization occurs in man and indicates that mosquito-bite whealing is a classic type I allergic reaction. The delayed mosquito-bite papules seem to be cutaneous late-phase reactions mediated by eosinophils or they could also represent type IV lymphocyte-mediated immune reactions. People living in heavily infested areas such as Lapland frequently acquire tolerance to mosquito bites, and seem to have negligible levels of IgE but high amounts of IgG4 antisaliva antibodies. Desensitization treatment is a theoretical possibility but prophylactically given cetirizine, an H1-blocking antihistamine, has been shown to be helpful for people suffering from mosquito bites.
An alphavirus isolated from Culiseta mosquitoes has been associated with Ockelbo disease, an exanthema arthralgia syndrome occurring in Sweden. The isolate was made from mosquitoes collected in Edsbyn (central Sweden), an area with considerable Ockelbo disease morbidity. This isolate proved to be indistinguishable from Sindbis virus by complement-fixation and hemagglutination-inhibition tests, and was antigenically related to Sindbis in plaque reduction neutralization tests. Patients with Ockelbo disease developed neutralizing antibodies to the virus in their convalescent sera, suggesting that it is the etiologic agent of the disease.
Animals that deliver a toxic secretion through a wound or to the body surface without a wound are considered venomous and toxungenous, respectively. Hematophagous insects, such as mosquitoes (Aedes spp.), meet the criteria for venomous, and some endoparasitic insects, such as warble flies (Hypoderma tarandi), satisfy the definition for toxungenous. The impacts of these insects on their hosts are wide ranging. In the Arctic, their primary host is the most abundant ungulate, the caribou (Rangifer tarandus). The most conspicuous impacts of these insects on caribou are behavioral. Caribou increase their movements during peak insect harassment, evading and running away from these parasites. These behavioral responses scale up to physiological effects as caribou move to less productive habitats to reduce harassment which increases energetic costs due to locomotion, reduces nutrient intake due to less time spent foraging, and can lead to poorer physiological condition. Reduced physiological condition can lead to lower reproductive output and even higher mortality rates, with the potential to ultimately affect caribou demographics. Caribou affect all trophic levels in the Arctic and the processes that connect them, thus altering caribou demographics could impact the ecology of the region. Broadening the definitions of venomous and toxungenous animals to include hematophagous and endoparasitic insects should not only generate productive collaborations among toxinologists and parasitologists, but will also lead to a deeper understanding of the ecology of toxic secretions and their widespread influence.