Prevalence, intensity and population dynamics of hard ticks (Acari: Ixodidae) on sheep in the humid tropics of Mexico

Hard Tick Species Parasitism Levels in Domestic Ruminants with Their Distribution and Role as Vectors: A Detailed Global Meta-analysis and Systematic Review

PURPOSE

This comprehensive global meta-analysis reviews the parasitism levels of tick genera and species, life stages, seasonality, attachment sites, the global mean ranks of tick species parasitism rates and records, and their distribution and role as vectors.

METHODS

From the 418 papers identified, 390 papers were selected to become part of the study.

RESULTS

The genera recorded as infesting domestic ruminants were Rhipicephalus (42 species), Haemaphysalis (32 species), Hyalomma (19 species), Amblyomma (18 species), Ixodes (10 species), Dermacentor (8 species), Margaropus and Nosomma (1 species). Globally, domestic ruminants are more infested by adult females and males than by the nymphal and larval stages of the tick species. The global tick species parasitism levels at the attachment sites of domestic ruminants were, in order, tail and anal region, neck and dewlap, scrotum or udder, ear region, thigh and abdomen, and dorsal surface.

CONCLUSIONS

Among 131 species of eight genera of hard ticks recorded infesting domestic ruminants, 42 species had mean ranks of tick species parasitism rates up to 10%, and 37 species had mean ranks of tick species parasitism up to 10 records. Briefly, the higher the indexes of tick species parasitism rates and records, the more important their role as vectors. In addition, the majority of them are found among tick species-infested humans with nearly high ranks of tick species parasitism rates and records that double their medical, veterinary, and zoonotic importance to be the most common vectors and reservoirs of bacterial, protozoan, and viral pathogenic microorganisms, causing severe infectious diseases, and as a result, can be more dangerous to humans and domestic ruminants.

HARD TICKS (ACARI: IXODIDAE) INFESTING ARABIAN CAMELS (CAMELUS DROMEDARIUS) IN MEDINA AND QASSIM, SAUDI ARABIA

Ixodid ticks are hematophagous obligatory ectoparasites that occur worldwide and transmit pathogens to humans and other vertebrates, causing economic livestock losses. The Arabian camel (Camelus dromedarius Linnaeus, 1758) is an important livestock animal in Saudi Arabia that is vulnerable to parasitism by ticks. The diversity and intensity of ticks on Arabian camels in certain localities in the Medina and Qassim regions of Saudi Arabia were determined. One hundred forty camels were examined for ticks, and 106 were infested (98 females, 8 males). A total of 452 ixodid ticks (267 males, 185 females) were collected from the infested Arabian camels. The tick infestation prevalence was 83.1% and 36.4% in female and male camels, respectively (female camels harbored significantly more ticks than did male camels). The recorded tick species were Hyalomma dromedarii Koch, 1844 (84.5%); Hyalomma truncatum Koch, 1844 (11.1%); Hyalomma impeltatum Schulze and Schlottke, 1929 (4.2%); and Hyalomma scupense Schulze, 1919 (0.22%). Hyalomma dromedarii was the predominant tick species in most regions, with a mean intensity of 2.15 ± 0.29 ticks/camel (2.5 ± 0.53 male ticks/camel, 1.8 ± 0.21 female ticks/camel). The proportion of male ticks was higher than that of female ticks (59.1 vs. 40.9%). To the best of our knowledge, this is the first survey of ixodid ticks on Arabian camels in Medina and Qassim, Saudi Arabia.

Amblyomma mixtum free-living stages: Inferences on dry and wet seasons use, preference, and niche width in an agroecosystem (Yopal, Casanare, Colombia)

The formulation of effective control strategies for any pest species generally involves the study of habitat use and preference and niche width in anthropogenically transformed natural landscapes. We evaluated whether the use, habitat preference, and niche range of the Amblyomma mixtum tick changed between stages, habitats, and seasonality (dry-wet seasons 2019) on a farm in Yopal (Casanare, Colombia). The presence and relative abundance of free-living larvae, nymphs, and adults was quantified in four different habitats according to the type of vegetation cover (Riparian Forest, Cocoa Crop, King Grass Crop, and Star Grass Paddock). Habitat availability was estimated, environmental variables were analyzed, and various indices of habitat use and preference, and niche width were calculated. A. mixtum's habitat use and preference, and niche width changed between stages, habitat types, and time of the year. The total abundance of A. mixtum was an order of magnitude greater in the dry season than the wet season. In the dry season, all stages used all habitats, while A. mixtum adults used all the habitats in both seasons. In the dry season, nymphs and larvae preferred three out of the four habitats, while adults preferred the King Grass Crop. In the wet season, nymphs and larvae preferred two habitats, whereas the adults preferred the King Grass Crop. The value of the niche width index was high for larvae, nymphs, and adults in the dry season, while it was high only for adults in the wet season. Thus, A. mixtum's vast environmental tolerance and niche breadth allows the species to use and colonize changing habitats (unstable or temporary) with fluctuating environmental conditions (e.g., King Grass Crop), potentially keeping a stable population over time and making it an extremely resistant species. However, the wet flooding season in Yopal may exceed A. mixtum's stages' tolerances.

Molecular detection of Rickettsia amblyommatis and Rickettsia parkeri in ticks collected from wild pigs in Campeche, Mexico

Tick-borne rickettsioses are caused at least by 15 species of Rickettsia of the Spotted fever group, which represent a major emerging and re-emerging public health problem worldwide. Some of these microorganisms have complex cycles involving the interaction of multiple species of ticks and wild and domestic mammals. Rickettsia infection was investigated in ticks collected from wild pigs at six localities in southeastern Mexico. We collected and tested 196 ticks belonging to four species, including Amblyomma maculatum, Amblyomma mixtum, Amblyomma ovale and Riphicephalus microplus, from 13 of 20 (65%) wild pigs sampled. Overall, Rickettsia DNA was detected in 13.8% of ticks tested (10 ♂ and 17 ♀). Of the 27 Rickettsia-positive ticks, six were A. maculatum, and 21 A. mixtum. Sequencing and phylogenetic analysis of the gltA and ompB genes revealed the presence of Rickettsia parkeri sensu stricto in one female A. maculatum and Rickettsia amblyommatis in five A. maculatum (2 ♂, 3 ♀) and 21 A. mixtum ticks (8 ♂, 13 ♀). The finding of two rickettsial agents in ticks collected from a wild pig population that is regularly captured and kept in captivity or hunted as a source of food raises concern about potential disease transmission to humans and domestic animals. However, more investigations are needed to further understand the ecology of Rickettsia species in free-ranging animals and their implications for human health.

Morphometrics of Amblyomma mixtum in the State of Veracruz, Mexico

The tick Amblyomma mixtum is an ectoparasite of veterinary and public health importance because of its role as a vector of zoonotic pathogens. However, little is known about A. mixtum intraspecific variability and if morphological differentiation exists between populations across its geographic range. This study aimed to determine by electron microscopy the morphological variability of A. mixtum populations in the state of Veracruz, which has a large livestock population among states in Mexico. Forty male and 40 female A. mixtum collected from the 10 natural regions of Veracruz state were analyzed microscopically to accomplish main component analysis for each sex. Clusters were calculated with the out-tree method and a dendrogram produced to group the specimens according to their morphometric characteristics. Using 10 main components, 77% of the morphological variation of the ticks was explained. This is a reflection of scarce intraspecific variation between females. The dendogram for females grouped six clusters of specimens with similar characteristics. Morphometric variability in males was described using eight main components. Limited intraspecific variation was also observed between males. In males, the dendogram yielded six groups with similar morphometric characteristics. Morphometric analyses confirmed that the only species from the Amblyomma cajennense complex that are parasites to livestock in Veracruz state is A. mixtum. The eryxenous nature of A. mixtum combined with the frequent movement of livestock hosts may contribute to the apparent homogeneous phenotype of this tick species in Mexico.

Genetic structure analysis of Amblyomma mixtum populations in Veracruz State, Mexico

Amblyomma mixtum Koch, 1844 parasitizes livestock, humans, and wildlife in Mexico. However, information on population genetics for this tick species in the country is missing. Tick samples were collected from livestock in ten regions across the state of Veracruz (22°28'N, 17°09'S, 93°36'E, 98°39'W) to analyze the genetic structure of   A. mixtum populations. Ticks were morphologically identified using taxonomic keys. In order to test the intra-specific variability of A. mixtum fragments of the mitochondrial gene 16S-rRNA and cytochrome oxidase subunit 1 (COI) were amplified. Ninety-six sequences were amplified from the 50 specimens' analyzed (96% amplification success). Eleven haplotypes were detected in 16S-rRNA gene and 10 more for COI. Neutrality tests showed negative results in most of the locations analyzed, which is indicative of an excess of recently derived haplotypes. However, these results were not statistically significant. Minimal union network analysis revealed that there is no separation of populations by geography, and that there is an overlap of several haplotypes among diverse populations. Significant genetic differentiation was not detected in the A. mixtum populations sampled in the state of Veracruz, Mexico, this may be due to the frequent movement of livestock hosts. This is the first report on the genetic structure of A. mixtum populations in Mexico.