Detection of IgG against Rickettsia typhi: a population-based study in southern Kazakhstan

Uvod. Rickettsia typhi svrstava se u skupinu pjegavih tifusa i uzrokuje endemski tifus. Slučajevi endemskog tifusa i seropozitivnosti na R. typhi zabilježeni su u susjednoj Kini i Rusiji. Međutim, o endemskom tifusu u Kazahstanu se malo zna. Svrha ove studije bila je procijeniti prevalenciju IgG protutijela na R. typhi u populaciji južne regije Kazahstana. Metode. U istraživanje je uključeno ukupno 253 osoba (142 žena, 111 muškaraca) u dobi od 1 do 71 godine. Detekcija serumskih IgG protutijela na R. typhi provedena je imunoenzimskim ELISA testom. Rezultati. Ukupna seropozitivnost na R. typhi iznosila je 34,4%. Najveća seroprevalencija od 91,8% zabilježena je u regiji Turkestan. Najniža seropozitivnost od 6,1% otkrivena je u selu Lepsinsk, regija Almaty. Seroprevalencija se nije značajno razlikovala prema spolu. Seropozitivnost kod odraslih pojedinaca nije bila značajno povezana s dobi, ali pozitivni rezultati nisu otkriveni u dobnoj skupini djece mlađe od 14 godina. Zaključak. Dobiveni rezultati potvrđuju aktivnu cirkulaciju R. typhij u regijama Turkestan i Almaty u Kazahstanu. Podaci ukazuju na hitnu potrebu za daljnjim istraživanjima čiji je cilj procijeniti klinički učinak R. typhi u južnoj regiji Kazahstana.Background. Rickettsia typhi belongs to the typhus group of rickettsiae and causes endemic typhus. Cases of endemic typhus and seropositivity to R. typhi have been reported in the neighbouring China and Russia. However, little is known of the endemic typhus in Kazakhstan. The purpose of this study was to evaluate the prevalence of IgG antibodies to R. typhi in the population of southern region of Kazakhstan. Methods. A total of 253 individuals (142 women, 111 men) aged from 1 to 71 years were recruited into the study. Detection of serum IgG antibodies against R. typhi was performed by enzyme-linked immunosorbent assay (ELISA). Results. The overall R. typhi seropositivity has reached 34.4%. The highest seroprevalence of 91.8% was recorded in the Turkestan Region. The lowest seropositivity of 6.1% was detected in the village Lepsinsk, Almaty Region. The seroprevalence did not differ significantly between genders. Seropositivity in adult individuals was not significantly associated with age, but positive results were not detected in the age group of children under 14 years. Conclusion. The obtained results confirm active circulation of R. typhi in the Turkestan and Almaty Regions of Kazakhstan. The data indicate an urgent need for further studies aimed to evaluate the clinical impact caused by R. typhi in the southern region of Kazakhstan

Vectors, molecular epidemiology and phylogeny of TBEV in Kazakhstan and central Asia

BACKGROUND: In the South of Kazakhstan, Almaty Oblastʼ (region) is endemic for tick-borne encephalitis, with 0.16–0.32 cases/100,000 population between 2016–2018. The purpose of this study was to determine the prevalence and circulating subtypes of tick-borne encephalitis virus (TBEV) in Almaty Oblastʼ and Kyzylorda Oblastʼ. METHODS: In 2015 we investigated 2341 ticks from 7 sampling sites for the presence of TBEV. Ticks were pooled in 501 pools and isolated RNA was tested for the presence of TBEV by RT-qPCR. For the positive samples, the E gene was amplified, sequenced and a phylogenetic analysis was carried out. RESULTS: A total of 48 pools were TBEV-positive by the RT-qPCR. TBEV-positive ticks were only detected in three districts of Almaty Oblastʼ and not in Kyzylorda Oblastʼ. The positive TBEV pools were found within Ixodes persulcatus, Haemaphysalis punctata and Dermacentor marginatus. These tick species prevailed only in Almaty Oblastʼ whereas in Kyzylorda Oblastʼ Hyalomma asiaticum and D. marginatus are endemic. The minimum infection rates (MIR) in the sampling sites were 4.4% in Talgar, 2.8% in Tekeli and 1.1% in Yenbekshikazakh, respectively. The phylogenetic analysis of the generated sequences indicates that TBEV strains found in Almaty Oblastʼ clusters in the Siberian subtype within two different clades. CONCLUSIONS: We provided new data about the TBEV MIR in ticks in Almaty Oblastʼ and showed that TBEV clusters in the Siberian Subtype in two different clusters at the nucleotide level. These results indicate that there are different influences on the circulating TBEV strains in south-eastern Kazakhstan. These influences might be caused by different routes of the virus spread in ticks which might bring different genetic TBEV lineages to Kazakhstan. The new data about the virus distribution and vectors provided here will contribute to an improvement of monitoring of tick-borne infections and timely anti-epidemic measures in Kazakhstan