Evaluation of two artificial infection methods of live ticks as tools for studying interactions between tick-borne viruses and their tick vectors

Up to 170 tick-borne viruses (TBVs) have been identified to date. However, there is a paucity of information regarding TBVs and their interaction with respective vectors, limiting the development of new effective and urgently needed control methods. To overcome this gap of knowledge, it is essential to reproduce transmission cycles under controlled laboratory conditions. In this study we assessed an artificial feeding system (AFS) and an immersion technique (IT) to infect Ixodes ricinus ticks with tick-borne encephalitis (TBE) and Kemerovo (KEM) virus, both known to be transmitted predominantly by ixodid ticks. Both methods permitted TBEV acquisition by ticks and we further confirmed virus trans-stadial transmission and onward transmission to a vertebrate host. However, only artificial feeding system allowed to demonstrate both acquisition by ticks and trans-stadial transmission for KEMV. Yet we did not observe transmission of KEMV to mice (IFNAR−/− or BALB/c). Artificial infection methods of ticks are important tools to study tick-virus interactions. When optimally used under laboratory settings, they provide important insights into tick-borne virus transmission cycles.

Epidemiological Community and Differences of Transmissive Infections in Astrakhan Region

Relevance. The territory of the Astrakhan region hosts natural foci of severe infections of arbovirus etiology – Crimean-Congo hemorrhagic fever (CCHF) and Astrakhan fever (spotted fever resembling the Mediterranean spotted fever, Astrakhan spotted fever (ASF). The long-term average incidence of CCHF and ASF in the Astrakhan region is to 11 and 135 times higher, respectively, than the average incidence in the Russian Federation. Aims. To present, based on epidemiological data, a comparative characterization of transmissible infections of CCHF and ASF in the Astrakhan region. Materials & Methods. The main method of the study was epidemiological. The data for 2000−2016 of primary medical documentation Ф.058/у «Emergency notification of infectious disease, food, acute occupational poisoning, unusual reaction to vaccination», federal statistical observation Ф. 2 «Information on infectious and parasitic diseases», Ф. 357/у «Epidemiological examination card of infectious disease focus», Ф. .003/у «Medical card of inpatient patient», presented by Center of hygiene and epidemiology in Astrakhan region. For retrospective epidemiological analysis, we studied the absolute and intensive morbidity indicators (per 100 ths population), by age, professional groups, and among the urban and rural population. Based on the average long-term morbidity indicators of the population, a mapping of the territory of the Astrakhan region was carried out. The influence of natural and climatic conditions on the epidemic process of CCHF and ASF was assessed by meteorological data (amount of precipitation, air temperature, etc.). Materials of long-term observation over 11 districts of Astrakhan region and Astrakhan city were analyzed, including data on the spread of Ixodid ticks, population contact with them (according to the attendance of people to treatment-and-prophylactic organizations of the region). Statistical data processing was carried out using the method of straight-line alignment of dynamic series of morbidity indicators, calculation of the average annual rate of decrease/increase. Correlation analysis was used to assess the direction and strength of the relationship between the indicators, and quantitative dependence between epidemic process characteristics. Differences between the indicators were considered to be reliable if p < 0.05. Results. During the analyzed period 151 cases of CCHF and 3951 cases of ASF were identified. By 2016. CCHF was registered in all 11 districts of the region and the area of foci covered 44,000 km2 and 44,100 km2, respectively. There are no differences significantly affecting the epidemic process of CCHF and ASF, so preventive measures are mainly aimed at controlling the vectors of the pathogens of these infections. The comprehensive study of the territory of Astrakhan region carried out in 2000–2016 revealed expansion of CCHF and ASF areal of disease (by 11.8% and 23.4% respectively) and determined the territories with the highest risk of infection, which allowed to increase and redistribute the volumes of acaricide treatments of the territories with the highest infection risk and ensure the decrease of CCHF and ASF morbidity rates. Conclusion. As a result of the comprehensive study conducted in 2000–2016 in the territory of Astrakhan region, the expansion of CCHF and ASF areal of disease was revealed (by 11.8% and 23.4% respectively) and the areas of highest infection risk were identified, which allowed to increase and redistribute the volume of acaricide treatments of the areas of highest infection risk and ensure the reduction of CCHF and ASF morbidity.

Utilizing two Borrelia bavariensis isolates naturally lacking the PFam54 gene array to elucidate the roles of PFam54-encoded proteins

Lyme borreliosis is the most common vector-borne disease in the Northern hemisphere, caused by spirochetes belonging to the Borrelia burgdorferi sensu lato ( Bb sl) species complex which are transmitted by ixodid ticks. Bb sl species produce a family of proteins on the linear plasmid 54 (PFam54), some of which confer the functions of cell adhesion and inactivation of complement, the first line of host defense. However, the impact of PFam54 in promoting Bb sl pathogenesis remains unclear because of the hurdles to simultaneously knock out all PFam54 proteins in a spirochete. Here, we describe two Borrelia bavariensis ( Bbav ) strains, PBN and PNi, isolated from patients naturally lacking PFam54 but maintaining the rest of the genome with greater than 95% identity to the reference Bbav strain PBi. We found that PBN and PNi less efficiently survive in human serum than PBi. Such defects were restored by introducing two Bbav PFam54 recombinant proteins, BGA66 and BGA71, confirming the role of these proteins in providing complement evasion of Bbav . Further, we found that all three strains remain detectable in various murine tissues 21 days post subcutaneous infection, supporting the non-essential role of Bbav PFam54 in promoting spirochete persistence. This study identified and utilized isolates deficient in PFam54 to associate the defects with the absence of these proteins, building the foundation to further study the role of each PFam54 protein in contributing to Bb sl pathogenesis. Importance To establish infections, Lyme borreliae utilize various means to overcome the host’s immune system. Proteins encoded by the PFam54 gene array play a role for spirochete survival in vitro and in vivo . Moreover, this gene array has been described in all currently available Lyme borreliae genomes. By investigating the first two Borrelia bavariensis isolates naturally lacking the entire PFam54 gene array, we showed that both patient isolates display an increased susceptibility to human serum, which can be rescued in the presence of two PFam54 recombinant proteins. However, both isolates remain infectious to mice after intradermal inoculation suggesting the non-essential role of PFam54 during long-term but may differ slightly in the colonization of specific tissues. Furthermore, these isolates show high genomic similarity to type-strain PBi (>95%) and could be used in future studies investigating the role of each PFam54 protein in Lyme borreliosis pathogenesis.

Reproductive features of the biology of some ticks of the family Ixodidae Murray, 1877 widespread in the southeast of the North Caucasus

The purpose of the research is study of some reproductive characteristics of the biology of ticks of the family Ixodidae which are widespread in the southeast of the North Caucasus.Materials and methods. In 2000–2010, 9 series of experiments were carried out in the conditions of the plain belt in Dagestan. The first, second, and third series of experiments were intended to find out the duration of the tick searching for a place to fix on the animal, the duration of the skin incised and the proboscis inserted into the wound, and the engorgement duration; and the fourth series was intended to clarify the tick wintering on the animal. Such experiments were performed on two-year-old calf bulls on the Educational and Experimental Farm of the Dagestan State Agrarian University with Boophilus annulatus, Rhipicephalus bursa, Hyalomma detritum, H. scupense, and H. anatolicum in 2000. Five hungry adult female ticks were placed onto all 5 calf bulls in the middle third of the neck. We conducted experiments on searching for a place for egg-laying, egg-laying duration in the environment, number of eggs in a clutch, duration of the larva formed and the hatching rate, distance of the larvae from the hatching place, and larvae death rate in five specially equipped sites of pastures of 1 m2 . Five adult female ticks of B. annulatus, R. bursa, H. detritum, H. scupense, and H. anatolicum were placed after engorgement in each biological site.Results and discussion. Ixodid ticks perform their natural physiological functions associated with feeding and reproduction with significant time fluctuations. The search for a place to fix on the animal took 4–8 hours; the skin incised and proboscis inserted in the wound took 2–5 hours; the engorgement took 4–6 hours; the search for an egg-laying place took 10– 22 hours; the egg-laying duration in the environment was 18–23 hours; the number of eggs in a clutch was 4–13K; the duration of the larva formed and the hatching rate was 10–15 days and 58.0–75% respectively; the distance of the larva from the hatching place was 0.5–1.5 m; death rate of the larva in captivity was 100%; and the tick wintering on the animal was near the neck, ears, in the dewlap, the flank and the udder. These features are typical for the analyzed tick species in the southeast of the North Caucasus and, probably, for other taxa of these genera.

Studies of ticks of the genus Dermacentor (Acari; Ixodidae) on the natural occurrence of tularemia pathogen in the conditions of the Central Pre-Caucasian region

The purpose of the research is the assessment of the Francisella tularensis occurrence in nature in ticks of the genus Dermacentor; understanding the physiological age in terms of tick infection with tularemia pathogen.Materials and methods. For the period from 2015 to 2019, we examined 8449 specimens of Dermacentor marginatus (916 pools), 8674 specimens of D. reticulatus (705 pools), and 109 specimens of D. niveus (40 pools) for tularemia infection. To assess the dependence of tularemia pathogen found in ticks of different physiological ages, we examined 2440 specimens of D. marginatus (360 pools), and 3349 specimens of D. reticulatus (412 pools) for the period from 2016 to 2019. Studies of ixodid ticks infected with tularemia pathogen were performed by the Natural Focal Infection Laboratory of the Stavropol Anti-Plague Institute. Pools of ixodid ticks were examined for the pathogen DNA of tularemia using reagent kits for identifying Francisella tularensis DNA by polymerase chain reaction with fluorescence hybridization of results recorded in real time.Results and discussion. The infection rate of the tularemia pathogen in ticks in the Central Pre-Caucasian region ranged from 0.044–1.127% in D. marginatus and 0.035–1.455% in D. reticulatus in different years. The greatest number of F. tularensis was isolated from the III physiological age ticks. For D. reticulatus ticks, no statistically significant dependence of the detected tularemia pathogen on physiological age was found.

Ticks and Tick-Borne Pathogens Abound in the Cattle Population of the Rabat-Sale Kenitra Region, Morocco

Tick-borne pathogens cause the majority of diseases in the cattle population in Morocco. In this study, ticks were collected from cattle in the Rabat-Sale-Kenitra region of Morocco and identified morphologically, while tick-borne pathogens were detected in cattle blood samples via polymerase chain reaction assay and sequencing. A total of 3394 adult ixodid ticks were collected from cattle and identified as eight different tick species representing two genera, Hyalomma and Rhipicephalus. The collected ticks consisted of Hyalomma marginatum, Hyalomma anatolicum excavatum, Rhipicephalus sanguineus sensu lato, Rhipicephalus bursa, Hyalomma detritum, Hyalomma lusitanicum, Hyalomma dromedarii, and Hyalomma impeltatum. The overall prevalence of tick-borne pathogens in blood samples was 63.8%, with 29.3% positive for Babesia/Theileria spp., 51.2% for Anaplasma/Ehrlichia spp., and none of the samples positive for Rickettsia spp. Sequencing results revealed the presence of Theileria annulata, Babesia bovis, Anaplasma marginale, Theileria buffeli, Theileria orientalis, Babesia occultans, Anaplasma phagocytophilum, Anaplasma capra, Anaplasma platys, Anaplasma bovis, Ehrlichia minasensis, and one isolate of an unknown bovine Anaplasma sp. Crossbreeds, females, older age, and high tick infestation were the most important risk factors for the abundance of tick-borne pathogens, which occurred most frequently in Jorf El Melha, Sidi Yahya Zaer, Ait Ichou, and Arbaoua locations.

Molecular evidence of Anaplasma phagocytophilum in olive baboons and vervet monkeys in Kenya

Background Nonhuman primates (NHPs) play a significant role in zoonotic spill-overs, serving as either reservoirs, or amplifiers, of multiple neglected tropical diseases, including tick-borne infections. Anaplasma phagocytophilum are obligate intracellular bacteria of the family Anaplasmatacae, transmitted by Ixodid ticks and cause granulocytic anaplasmosis (formerly known as Human Granulocytic Ehrlichiosis (HGE)) in a wide range of wild and domestic mammals and humans too. The aim of this study was to determine whether Anaplasma phagocytophilum was circulating in olive baboons and vervet monkeys in Laikipia County, Kenya. Results Some 146 blood samples collected from olive baboons and 18 from vervet monkeys from Mpala Research Center and Ol jogi Conservancy in Laikipia County were screened for the presence of Anaplasma species using conventional Polymerase Chain Reaction (PCR), and then A. phagocytophilum was confirmed by sequencing using conventional PCR targeting 16S rRNA. This study found an overall prevalence of 18.3% for Anaplasma species. DNA sequences confirmed Anaplasma phagocytophilum in olive baboons for the first time in Kenya. Conclusion This study provides valuable information on the endemicity of A. phagocytophilum bacteria in olive baboons in Kenya. Future research is needed to establish the prevalence and public health implications of zoonotic A. phagocytophilum isolates and the role of nonhuman primates as reservoirs in the region.

The Global Emergence of Human Babesiosis

Babesiosis is an emerging tick-borne disease caused by intraerythrocytic protozoa that are primarily transmitted by hard-bodied (Ixodid) ticks and rarely through blood transfusion, perinatally, and organ transplantation. More than 100 Babesia species infect a wide spectrum of wild and domestic animals worldwide and six have been identified as human pathogens. Babesia microti is the predominant species that infects humans, is found throughout the world, and causes endemic disease in the United States and China. Babesia venatorum and Babesia crassa-like agent also cause endemic disease in China. Babesia divergens is the predominant species in Europe where fulminant cases have been reported sporadically. The number of B. microti infections has been increasing globally in recent decades. In the United States, more than 2000 cases are reported each year, although the actual number is thought to be much higher. In this review of the epidemiology of human babesiosis, we discuss epidemiologic tools used to monitor disease location and frequency; demographics and modes of transmission; the location of human babesiosis; the causative Babesia species in the Americas, Europe, Asia, Africa, and Australia; the primary clinical characteristics associated with each of these infections; and the increasing global health burden of this disease.