Upscaling the surveillance of tick-borne pathogens in the French Caribbean Islands

Despite the high burden of vector-borne disease in (sub)tropical areas, few information are available regarding the diversity of tick and tick-borne pathogens circulating in the Caribbean. Management and control of vector-borne disease require actual epidemiological data to better assess and anticipate the risk of (re)emergence of tick-borne diseases in the region. To simplify and reduce the costs of such large-scale surveys, we implemented a high-throughput microfluidic real-time PCR system suitable for the screening of the main bacterial and parasitic genera involved in tick-borne disease and potentially circulating in the area. We used the new screening tool to perform an exploratory epidemiological study on 132 adult specimens of Amblyomma variegatum and 446 of Rhipicephalus microplus collected in Guadeloupe and Martinique. Not only the system was able to detect the main pathogens of the area—Ehrlichia ruminantium, Rickettsia africae, Anaplasma marginale, Babesia bigemina and Babesia bovis—but the system also provided evidence of unsuspected microorganisms in Caribbean ticks, belonging to the Anaplasma, Ehrlichia, Borrelia and Leishmania genera. Our study demonstrated how high-throughput microfluidic real-time PCR technology can assist large-scale epidemiological studies, providing a rapid overview of tick-borne pathogen and microorganism diversity, and opening up new research perspectives for the epidemiology of tick-borne pathogens

Demonstration of vermicules of Babesia species in haemolymph smears of Amblyomma variegatum in Nigeria

The present study was conducted to investigate the presence of developmental stage (s) of Babesia species in Amblyomma variegatum. A total of 137 Amblyomma variegatum ticks (85 males and 52 females) were examined by haemolymph smears. Out of the examined male ticks, there were 41 nymphs and 44 adults. The female ticks were 23 nymphs and 29 engorged adults. Sixteen adult males and nine nymphs were positive for vermicules of Babesia species but only eight femalesshowed structures similar to Babesia vermicules. The present study recommends conducting molecular and experimental studies to confirm the type of Babesia parasite in Amblyomma variegatum tick

High prevalence of <i>Rickettsia africae</i> variants in <i>Amblyomma variegatum</i> ticks from domestic mammals in rural western Kenya: implications for human health

Tick-borne spotted fever group (SFG) rickettsioses are emerging human diseases caused by obligate intracellular Gram-negative bacteria of the genus Rickettsia. Despite being important causes of systemic febrile illnesses in travelers returning from sub-Saharan Africa, little is known about the reservoir hosts of these pathogens. We conducted surveys for rickettsiae in domestic animals and ticks in a rural setting in western Kenya. Of the 100 serum specimens tested from each species of domestic ruminant 43% of goats, 23% of sheep, and 1% of cattle had immunoglobulin G (IgG) antibodies to the SFG rickettsiae. None of these sera were positive for IgG against typhus group rickettsiae. We detected Rickettsia africae–genotype DNA in 92.6% of adult Amblyomma variegatum ticks collected from domestic ruminants, but found no evidence of the pathogen in blood specimens from cattle, goats, or sheep. Sequencing of a subset of 21 rickettsia-positive ticks revealed R. africae variants in 95.2% (20/21) of ticks tested. Our findings show a high prevalence of R. africae variants in A. variegatum ticks in western Kenya, which may represent a low disease risk for humans. This may provide a possible explanation for the lack of African tick-bite fever cases among febrile patients in Kenya

Morphological and molecular characterization of Amblyomma variegatum (Acari: Ixodidae) ticks from Nigeria

The association of most tick-borne pathogens with specific tick species has made it imperative that proper identification and characterization of such tick vectors is necessary for the purpose of developing effective tick and tick-borne control strategies. This study was undertaken to identify and characterize Amblyomma species ticks collected from cattle in Plateau State, North-Central, Nigeria. They were morphologically identified using diagnostic characters. Further confirmation and characterization was done genetically using a 460bp-long partial fragment of the 16S rRNA gene amplified by polymerase chain reaction (PCR). The amplified fragment was cloned and sequenced for the phylogenetic dendogram. All the examined ticks were identified as A. variegatum which was confirmed by 16S rRNA gene sequences analysis, and phylogenetic inferences showed a 99% similarity and grouping to A. variegatum of African origin. However, the A. variegatum sequences from Nigeria were clustered into 2 groups, but formed a distinct clade from the A. variegatum sequence from Ethiopia. This study was able to conclusively identify and characterize A. variegatum ticks from the study areas by utilizing morphology and molecular genotyping based on sequencing of the 16S rRNA gene.Keywords: Amblyomma variegatum, Morphology, 16S rRNA, PCR, Sequencin

Effects of exposing adults of Amblyomma variegatum to neem cake extracts in traps baited with semiochemicals under semi–laboratory conditions

The efficacy of a trap baited with an attractant blend comprising of attraction aggregation- attachment pheromone (AAAP), 1-octen-3-ol and CO2 and treated with Neem (Azadirachta indica) cake extracts (0.6% of azadirachtin) to attract and expose the ticks, Amblyomma variegatum (Fabricius) (Acari: Ixodidae) to the active constituents of the cake was evaluated in circular field plots.. Ticks were released at various distances from trap placed at the center of the plots. Ticks that arrived at the trap (and exposed to the extracts) and those in control plots were collected and their mortality was monitored in the laboratory over a three-week period. All concentrations of the neem extracts caused mortality of A. variegatum adults with highest mortality rate (97.8%) recorded in the concentration of 30 % of extracts. The mortality of the ticks was also dependent upon the time ticks were exposed to the extracts. The findings suggest the possibility of using semiochemicals-baited traps in combination with neem extracts for off-host control of these ticks in smallholder farms.Key words: Amblyomma variegatum, traps, Azadirachta indica, semiochemical