Ecology of Powassan Virus in the United States

Zoonotic viruses threaten the lives of millions of people annually, exacerbated by climate change, human encroachment into wildlife habitats, and habitat destruction. The Powassan virus (POWV) is a rare tick-borne virus that can cause severe neurological damage and death, and the incidence of the associated disease (Powassan virus disease) is increasing in the eastern United States. The mechanisms by which POWV is maintained in nature and transmitted to humans are complex and only partly understood. This review provides an overview of what is known about the vector species, vector-host transmission dynamics, and environmental and human-driven factors that may be aiding the spread of both the vector and virus.

Morphological aspects of immature stages of Migonemyia migonei (Diptera: Psychodidae, Phlebotominae) an important vector of Leishmaniosis in South America by scanning electron microscopy

We describe the immature stages of Migonemyia migonei, which is the vector of Leishmania (Viannia) braziliensis, the aetiological agent of cutaneous leishmaniasis in South America, and a putative vector of Leishmania infantum chagasi. Scanning Electron Microscopy (SEM) was used to refine the description of the structures of eggs, all instar larvae and pupa. The eggs have polygonal cells on the egg exochorion, and differences between larval and pupal chaetotaxy are highlighted. Different sensillary subtypes were observed in the larval stages, among the types trichoidea, basiconica, coelonica and campanoformia. These results contribute to the taxonomy of Mg. migonei and may contribute to future studies on the phylogeny of this important species vector.

Mosquitoes and their Medical Importance

Mosquitoes are vectors of many biologic agents of infection that range from bacteria, viral and parasitic infection. They cause diseases with high rate of morbidity and mortality. Plasmodium species are transmitted by the female anopheles genus and is the etiologic agent of malaria which is the major cause of absenteeism from work, school, reduced productivity, reduction in labour supply, illness and death in the tropics. Burkitts lymphoma is a malignancy that is higher in malaria endemic region. The genus culex and mansonia are the vectors of nematodes in the filariodea family. They cause spectrum of diseases ranging from eosinophillia, allergic lymphadenitis, lymphoedema and persistent infection could cause “elephantiasis”. The vector of zika virus is Aedes species. It is responsible for microcephaly in fetus of pregnant women infected in pregnancy. Yellow fever is a viral haemorrhagic fever caused by a flavivirus and transmitted also by the aedes species. Vector control with proper cleaning of the environment, individual use of insecticide treated net, use of prophylactic and prompt treatment of diseases caused by them are methods that have been suggested to reduce the mortality associated with the diseases caused by these mosquitoes.

BB0744 Affects Tissue Tropism and Spatial Distribution of Borrelia burgdorferi

Borrelia burgdorferi, the etiologic agent of Lyme disease, produces a variety of proteins that promote survival and colonization in both theIxodesspecies vector and various mammalian hosts. We initially identified BB0744 (also known as p83/100) by screening forB. burgdorferistrain B31 proteins that bind to α1β1integrin and hypothesized that, given the presence of a signal peptide, BB0744 may be a surface-exposed protein. In contrast to this expectation, localization studies suggested that BB0744 resides in the periplasm. Despite its subsurface location, we were interested in testing whether BB0744 is required for borrelial pathogenesis. To this end, abb0744deletion was isolated in aB. burgdorferistrain B31 infectious background, complemented, and queried for the role of BB0744 following experimental infection. A combination of bioluminescent imaging, cultivation of infected tissues, and quantitative PCR (qPCR) demonstrated that Δbb0744mutantB. burgdorferibacteria were attenuated in the ability to colonize heart tissue, as well as skin locations distal to the site of infection. Furthermore, qPCR indicated a significantly reduced spirochetal load in distal skin and joint tissue infected with Δbb0744mutantB. burgdorferi. Complementation withbb0744restored infectivity, indicating that the defect seen in Δbb0744mutantB. burgdorferiwas due to the loss of BB0744. Taken together, these results suggest that BB0744 is necessary for tissue tropism, particularly in heart tissue, alters the ability ofB. burgdorferito disseminate efficiently, or both. Additional studies are warranted to address the mechanism employed by BB0744 that alters the pathogenic potential ofB. burgdorferi.

Phylogenetic relationships of flaviviruses correlate with their epidemiology, disease association and biogeography

Phylogenetic analysis of the Flavivirus genus, using either partial sequences of the non-structural 5 gene or the structural envelope gene, revealed an extensive series of clades defined by their epidemiology and disease associations. These phylogenies identified mosquito-borne, tick-borne and no-known-vector (NKV) virus clades, which could be further subdivided into clades defined by their principal vertebrate host. The mosquito-borne flaviviruses revealed two distinct epidemiological groups: (i) the neurotropic viruses, often associated with encephalitic disease in humans or livestock, correlated with the Culex species vector and bird reservoirs and (ii) the non-neurotropic viruses, associated with haemorrhagic disease in humans, correlated with the Aedes species vector and primate hosts. Thus, the tree topology describing the virus–host association may reflect differences in the feeding behaviour between Aedes and Culex mosquitoes. The tick-borne viruses also formed two distinct groups: one group associated with seabirds and the other, the tick-borne encephalitis complex viruses, associated primarily with rodents. The NKV flaviviruses formed three distinct groups: one group, which was closely related to the mosquito-borne viruses, associated with bats; a second group, which was more genetically distant, also associated with bats; and a third group associated with rodents. Each epidemiological group within the phylogenies revealed distinct geographical clusters in either the Old World or the New World, which for mosquito-borne viruses may reflect an Old World origin. The correlation between epidemiology, disease correlation and biogeography begins to define the complex evolutionary relationships between the virus, vector, vertebrate host and ecological niche.