Anthology of Dirofilariasis in Russia (1915–2017)

Abstract

Dirofilariasis is a helminths vector-borne disease caused by two species of Dirofolaria—D. repens and D. immitis. The former is overwhelmingly associated with human dirofilariasis. The vector of the worm are mosquitoes of the family Culicidae (largely Culex, Aedes and Anopheles). The definitive hosts of Dirofilaria are dogs and to a lesser extent cats. Humans are an accidental host. A total of 1200 human cases caused by Dirofilaria were registered in the territory of the ex-USSR during the period 1915–2016. Zonal differences have been seen in the prevalence of infected dogs and mosquitoes. Studies undertaken in the southern part of the Russian Federation (RF) revealed the prevalence of Dirofilaria in dogs to be 20.8% with wild variations of larva density. Studies carried out in the central part of the RF found that the prevalence of parasites in dogs was 4.1%. Aedes mosquitoes were infected less than Culex and Anopheles mosquitoes. The latter were infected by D. repens more often than Culex and Aedes. Zonal differences were also traced in regard to Dirofilaria prevalence in humans, thus allowing identification of three zones of risk of infection (low, moderate, and stable), reflected in a series of constructed maps. Although Dirofilariasis was known on the territory of Russia from 1915, only sporadic cases of the disease were reported occasionally. Its number was showed an increasing trend only during the 1980s–1990s, reaching the level of hundreds of cases. The majority of cases were confined to the southern parts of Russia with geographic coordinates of 43°–45° on the northern latitude. Comparison of the timing of the global trend of climate warming during the 1990s with the temporal pattern of Dirofilaria on the territory of Russia during the same period demonstrated a close association between two phenomena. With the continuous process of global climate warming, the incidence of dirofilariasis both in man and dogs goes unabated exemplified by the territorial expansion of the disease northwards and eastwards attaining the latitude of 56°–57° on the northern latitude in the European and Asian parts of Russia. It appears that within the period of the last 20–25 years, the population at risk has doubled. Under these circumstances, dirofilariases in Russia should be considered as an emerging public health problem necessitating the establishment of a comprehensive epidemiological monitoring system with strong entomological and veterinary components. Based on the results obtained, an appropriate control intervention could be developed.

Emerging risk of Dirofilaria spp. infection in Northeastern Europe: high prevalence of Dirofilaria repens in sled dog kennels from the Baltic countries

“…Awareness of D. repens endemicity has helped to reduce prevalence of infection in some countries. Prevalence was also much higher in sled dogs than in other dogs/pet dogs, which is in agreement with previous studies on working dogs 21 , 32 . Sled dog kennels appear to constitute hotspots for D. repens transmission and thus establishment of new foci of infection.…”

“…In Belarus at least 80 human cases were recorded between 1997 and 2013 20 and Dirofilaria spp. have been found also in mosquitoes 49 .We did not identify D. repens infections among 11 dogs from Russia, but prevalence in different regions of Russia differs profoundly, and has been reported to be below 1% in the vicinity of Moscow (reviewed in: 21 ). Similarly, we did not find D. repens among the six sampled sled dogs from Finland, and to-date only a few cases of D. repens infections have been reported from this country, including one probably autochthonous human case in Southern Finland.…”

“…to Central Europe. Dirofilaria repens is now endemic in many countries in the region (Poland, Ukraine, Germany, Austria, Hungary, Netherlands) 6 – 17 , and is currently considered to be one of the fast spreading zoonoses in Central, Eastern and Northern Europe 2 , 4 , 18 – 21 . Not surprisingly, the number of published human cases is increasing also with reports on unusual localization of D. repens in human hosts 22 – 28 .…”

Human dirofilariosis in Austria: the past, the present, the future

“…This raises the concern that dirofilariosis will emerge as an endemic zoonotic parasitosis throughout Europe in the near future. In this context, an increase in human dirofilariosis cases has been reported throughout central and northern Europe, in particular in the Russian federation, Belarus and Ukraine, but also in Hungary, Bulgaria and Slovakia [ 2 , 14 , 31 – 35 ]. In addition, autochthonous cases of dirofilariosis in humans have been reported in countries neighboring Austria, such as Czechia, Germany, Hungary and Slovakia [ 36 – 40 ].…”

Human seroprevalence data indicate other factors than climatic conditions influencing dirofilariosis transmission in the Russian Federation

“…Although distribution of the disease appears to be cosmopolitan, human dirofilariosis cases are not homogenously reported throughout the world. According the latest estimates, one third of the human cases of dirofilariosis have been reported in the Russian Federation (more than 1400 cases) (Ermakova et al ., 2014; Kartashev et al ., 2015; ESDA, 2017; Moskvina & Ermolenko, 2018; Kondrashin et al ., 2020). However, it seems that only ‘the tip of the iceberg’ is portrayed since clinical cases only represent a part of human infections, and most cases remain asymptomatic, especially those cases that result in pulmonary nodules.…”