Tickborne Relapsing Fever, Jerusalem, Israel, 2004-2018

Prevalence of Lyme Disease and Relapsing Fever Borrelia spp. in Vectors, Animals, and Humans within a One Health Approach in Mediterranean Countries

The genus Borrelia has been divided into Borreliella spp., which can cause Lyme Disease (LD), and Borrelia spp., which can cause Relapsing Fever (RF). The distribution of genus Borrelia has broadened due to factors such as climate change, alterations in land use, and enhanced human and animal mobility. Consequently, there is an increasing necessity for a One Health strategy to identify the key components in the Borrelia transmission cycle by monitoring the human-animal-environment interactions. The aim of this study is to summarize all accessible data to increase our understanding and provide a comprehensive overview of Borrelia distribution in the Mediterranean region. Databases including PubMed, Google Scholar, and Google were searched to determine the presence of Borreliella and Borrelia spp. in vectors, animals, and humans in countries around the Mediterranean Sea. A total of 3026 were identified and screened and after exclusion of papers that did not fulfill the including criteria, 429 were used. After examination of the available literature, it was revealed that various species associated with LD and RF are prevalent in vectors, animals, and humans in Mediterranean countries and should be monitored in order to effectively manage and prevent potential infections.

Infection and seroprevalence of Borrelia persica in domestic cats and dogs in Israel

Background

Relapsing fever borreliosis is an infectious disease caused by bacteria of the genus Borrelia, inflicting recurrent episodes of fever and spirochetemia in humans. Borrelia persica, the causative agent of relapsing fever in Israel, is prevalent over a broad geographic area that extends from India to Egypt. It is transmitted by the soft tick Ornithodoros tholozani and causes disease in humans as well as domestic cats and dogs. The goal of this study was to survey domestic dogs and cats in Israel for infection with B. persica.

Methods

Blood, sera and demographic and clinical data were collected from dogs and cats brought for veterinary care in central Israel. PCR followed by DNA sequencing was used to detect B. persica DNA in blood samples, and an enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies reactive with B. persica antigens in sera from the same animals. This is the first serological survey of B. persica in dogs and the first survey for antibodies reactive with a relapsing fever Borrelia sp. in cats globally.

Results

Four of the 208 dogs (1.9%) and three of 103 cats (2.9%) sampled were positive by PCR for B. persica DNA, and 24 dogs (11.5%) and 18 cats (17.5%) were seropositive for B. persica antigen by ELISA. The ratio between PCR-positivity and seropositivity in both the dog and cat populations was 1:6. All four PCR-positive dogs and two of three PCR-positive cats were seronegative, suggesting a probable recent infection. Thrombocytopenia showed significant association with seropositivity in dogs (P = 0.003). In cats, anemia had a significant association with seropositivity (P = 0.0001), and thrombocytopenia was associated with the combined prevalence of seropositivity or PCR-positivity (P = 0.022).

Conclusions

Borrelia persica infection is more prevalent and widespread in domestic canine and feline populations in Israel than previously thought. Dogs and cats may play a role as reservoirs and sentinels for human infection. Precautions should be taken to prevent transfusion-transmitted infection between blood donor and recipient animals.

Graphic Abstract

Tick borne relapsing fever - a systematic review and analysis of the literature

Tick borne relapsing fever (TBRF) is a zoonosis caused by various Borrelia species transmitted to humans by both soft-bodied and (more recently recognized) hard-bodied ticks. In recent years, molecular diagnostic techniques have allowed to extend our knowledge on the global epidemiological picture of this neglected disease. Nevertheless, due to the patchy occurrence of the disease and the lack of large clinical studies, the knowledge on several clinical aspects of the disease remains limited. In order to shed light on some of these aspects, we have systematically reviewed the literature on TBRF and summarized the existing data on epidemiology and clinical aspects of the disease. Publications were identified by using a predefined search strategy on electronic databases and a subsequent review of the reference lists of the obtained publications. All publications reporting patients with a confirmed diagnosis of TBRF published in English, French, Italian, German, and Hungarian were included. Maps showing the epidemiogeographic mosaic of the different TBRF Borrelia species were compiled and data on clinical aspects of TBRF were analysed. The epidemiogeographic mosaic of TBRF is complex and still continues to evolve. Ticks harbouring TBRF Borrelia have been reported worldwide, with the exception of Antarctica and Australia. Although only molecular diagnostic methods allow for species identification, microscopy remains the diagnostic gold standard in most clinical settings. The most suggestive symptom in TBRF is the eponymous relapsing fever (present in 100% of the cases). Thrombocytopenia is the most suggestive laboratory finding in TBRF. Neurological complications are frequent in TBRF. Treatment is with beta-lactams, tetracyclines or macrolids. The risk of Jarisch-Herxheimer reaction (JHR) appears to be lower in TBRF (19.3%) compared to louse-borne relapsing fever (LBRF) (55.8%). The overall case fatality rate of TBRF (6.5%) and LBRF (4-10.2%) appears to not differ. Unlike LBRF, where perinatal fatalities are primarily attributable to abortion, TBRF-related perinatal fatalities appear to primarily affect newborns.

Transmission of the Human Relapsing Fever Spirochete Borrelia persica by the Argasid Tick Ornithodoros tholozani Involves Blood Meals from Wildlife Animal Reservoirs and Mainly Transstadial Transfer

Borrelia persica, transmitted by the argasid tick Ornithodoros tholozani, causes human tick-borne relapsing fever in the Middle East and Central Asia. Infection is acquired often when visiting tick-infested caves and reported to be transmitted mainly transovarially between ticks, occasionally infecting humans. To study the epidemiology of this infection, ticks were trapped in 24 caves in 12 geographic zones covering all of Israel and identified morphologically. DNA was extracted from larvae, nymphs, and adult stages from each location and PCR followed by DNA sequencing was performed to identify Borrelia infection, tick species, and tick blood meal sources. We collected 51,472 argasid ticks from 16 of 24 caves surveyed. We analyzed 2,774 O. tholozani ticks, and 72 (2.6%) from nine caves were PCR positive for B. persica Infection rates in male, female, and nymphal ticks (4.4%, 3%, and 3.2%, respectively) were higher than in larva (P < 0.001), with only 3 (0.04%) positive larvae. Presence of blood meal was associated with B. persica infection in ticks (P = 0.003), and blood meals of golden jackals, red foxes, and Cairo spiny mouse were associated with infection (P ≤ 0.043). PCR survey of 402 wild mammals revealed B. persica infection with the highest rates in social voles (22%), red foxes (16%), golden jackals (8%), and Cairo spiny mice (3%). In conclusion, although transovarial tick transmission of B. persica occurs at low levels, ticks apparently acquire infection mainly from wildlife canid and rodents and may eventually transmit relapsing fever borreliosis to humans who enter their habitat.IMPORTANCE Borrelia persica is a spirochete that causes tick-borne relapsing fever in humans in an area that spans from India to the Mediterranean. Until now, it was thought that the soft tick vector of this infection, Ornithodoros tholozani, is also its main reservoir and it transmits B. persica mostly transovarially between tick generations. This study showed that tick infection with B. persica is associated with feeding blood from wild jackals, foxes, and rodents and that transovarial transmission is minimal. Since O. tholozani ticks are found in isolated caves and ruins, it is assumed that wild canids who migrate over long distances have a major role in the transmission of B. persica between remote tick populations, and it is then maintained locally also by rodents and eventually transferred to humans during tick bites. Prevention of human infection could be achieved by restricting entrance of canines and humans to habitats with O. tholozani populations.