Sergey G. Medvedev

The paper explores the specific features of the fauna of fleas (Siphonaptera) that inhabit Karelia, as part of a larger geographic region comprising Northwest Russia, as well as Northern Europe – Fennoscandia. Information was primarily derived from summary reports. Data from AIS PARHOST1 on the world flea fauna, which has been supplemented constantly since 2001 and is hosted by the Zoological Institute RAS, were involved in the analysis. As of now, 28 flea species of 13 genera have been reported from Karelia, amounting to around 35% of the regional fauna and 13% of the flea fauna of Russia. The species occurring in Northwest Russia but not reported from Karelia can be split into two major groups. The first group includes parasites of those hosts whose fleas remain unstudied. The second group comprises fleas missing from the Karelian fauna as a result of vicariation.

This paper explores the specific features of the fauna of fleas (Siphonaptera) of Karelia, as part of a larger geographic region comprising Northwestern Russia and Fennoscandia. Our analysis included information from the available summary reviews and data from the PARHOST1 information analysis system on the world flea fauna, hosted by the Zoological Institute of the Russian Academy of Sciences and supplemented regularly since 2001. At present, 28 flea species of 13 genera have been recorded for Karelia, amounting to about 35% of the regional fauna and 13% of the flea fauna of Russia. The species occurring in Northwestern Russia but not found in Karelia can be divided into two major groups. The first group includes the parasites of those hosts whose fleas remain unstudied. The second group comprises the flea species that are absent in the Karelian fauna due to vicariation.

The distribution and host-parasite relationships of fleas of the genus Xenopsylla (Pulicidae) and their significance as plague vectors are analyzed. The worldwide distribution of plague foci and the role of this flea genus in pathogen circulation in various regions are considered. Xenopsylla fleas either act as the only main vectors or are included in the main vector pool in 114 out of 255 known natural plague foci around the world. Spontaneous infection with the plague microbe has been detected for 21 species of this genus, and 17 species are considered the main plague vectors in some foci. The flea X. cheopis is the most significant plague vector in Africa and South-East Asia.

The morphological basis and the reasons of differences between three classifications of the order of fleas (Siphonaptera), proposed in the second half of the 20th century, are analyzed.

In the last few years, there has been a dramatic increase in the number of discovered viruses that are transmitted by arthropods. Some of them are pathogenic for humans and mammals, and the pathogenic potential of others is unknown. The genus Orthoflavivirus belongs to the family Flaviviridae and includes arboviruses that cause severe human diseases with damage to the central nervous system and hemorrhagic fevers, as well as viruses with unknown vectors and viruses specific only to insects. The latter group includes Lammi virus, first isolated from a mosquito pool in Finland. It is known that Lammi virus successfully replicates in mosquito cell lines but not in mammalian cell cultures or mice. Lammi virus reduces the reproduction of West Nile virus during superinfection and thus has the potential to reduce the spread of West Nile virus in areas where Lammi virus is already circulating. In this work, we isolated Lammi virus from a pool of adult Aedes cinereus mosquitoes that hatched from larvae/pupae collected in Saint Petersburg, Russia. This fact may indicate transovarial transmission and trans-stadial survival of the virus.

In the review, the peculiarities of distribution, host-parasite relations, and significance as vectors of plague of the fleas of the genus Xenopsylla (Pulicidae) are analyzed. Spatial distribution of plague foci all over the world and the role of this genus fleas in circulation of the plague pathogen in various regions of the planet are considered. It is shown that out of at least 255 existing natural foci of plague around the world in which the circulation of the pathogen occurs independently of the other foci, in 114 foci the only main vectors or members of the main vector pool are the fleas of the genus Xenopsylla . Among 21 flea species of this genus found naturally infected with the plague microbe in nature, 17 species are considered as main vectors of this pathogen in a given number of foci; in Africa and Southeast Asia, the role of the flea X. cheopis is the most significant.

The combinations of structural characters previously used to substantiate various classifications of the order Siphonaptera are analyzed. The adaptive and phyletic morphotypes marking assemblages or phylogenetically close groups of flea families are considered.

The taxonomic diversity, distribution patterns, and host-parasite relationships of fleas of the genus Xenopsylla (Pulicidae) are analyzed. Six species and two subspecies of Xenopsylla, associated with gerbils in the territory of Russia and adjacent countries, are known as the main, accessory, or occasional vectors of the plague pathogen.

Results of the study of fleas associated with four insectivore and rodent species in northern Karelia are reported. Fleas were collected in August–September 2001, 2003–2004, 2006–2009, 2011, 2015, and 2019 in the environs of the White Sea Biological Station “Kartesh” (Zoological Institute of the Russian Academy of Sciences). The published data on distribution, host-parasite associations, and seasonal dynamics of eight flea species present in Northwestern European Russia are summarized.