Invasive cattle ticks in East Africa: morphological and molecular confirmation of the presence of Rhipicephalus microplus in south-eastern Uganda

Abstract

Background: Rhipicephalus microplus, an invasive tick species of Asian origin and the main vector of Babesia species, is considered one of the most widespread ectoparasites of livestock. The tick has spread from its native habitats on translocated livestock to large parts of the tropical world, where it has replaced some of the local populations of Rhipicephalus decoloratus ticks. Although the tick was reported in Uganda 70 years ago, it has not been found in any subsequent surveys. This study was carried out to update the national tick species distribution on livestock in Uganda as a basis for tick and tick-borne disease control, with particular reference to R. microplus.

Methods: The study was carried out in Kadungulu, Serere district, south-eastern Uganda, which is dominated by small scale livestock producers. All the ticks collected from 240 cattle from six villages were identified microscopically. Five R. microplus specimens were further processed for phylogenetic analysis and species confirmation.

Results: The predominant tick species found on cattle was Rhipicephalus appendiculatus (86.9 %; n = 16,509). Other species found were Amblyomma variegatum (7.2 %; n = 1377), Rhipicephalus evertsi (2.3 %; n = 434) and R. microplus (3.6 %; n = 687). Phylogenetic analysis of the 12S rRNA, 16S rRNA and ITS2 gene sequences of R. microplus confirmed the morphological identification.

Conclusions: It is concluded that R. microplus has replaced R. decoloratus in the sampled villages in Kadungulu sub-county, since the latter was not any longer found in this area. There is currently no livestock movement policy in force in Uganda, which could possibly limit the further spread of R. microplus ticks. Future surveys, but also retrospective surveys of museum specimens, will reveal the extent of distribution of R. microplus in Uganda and also for how long this tick has been present on livestock without being noticed.

Keywords: Rhipicephalus microplus; Serere district; Tick-borne diseases; Ticks; Uganda.

Fig. 1

Study area: Serere district, south-eastern Uganda. Red dots indicate the locations of the 6 villages from which 240 cattle were randomly selected and included in this study

Fig. 2

Morphological identification of R. microplus. a Female, ventral view (1, hypostomal teeth in a typical 4 + 4 column arrangement; 2, short palp of internal margin article 1 (lacks protuberance and is distinctly concave); 3, cornua). b Male, ventral view (4, distinctly small adenal plates; 5, ventral plate spurs (small accessory adanal plates); 6, caudal appendage; 7, genital aperture with a broad U-shape)

Fig. 3

Phylogenetic analysis based on the tick 12S ribosomal RNA gene. A phylogenetic tree based on 12S rDNA sequences. The tree was generated by the maximum likelihood method based on the Tamura 3-parameter model. The analysis involved 26 nucleotide sequences. Orange circles represent samples sequenced in this study

Fig. 4

Phylogenetic analysis based on the tick 16S ribosomal RNA gene. A phylogenetic tree based on 16S rDNA sequences. The tree was generated by the maximum likelihood method based on the Tamura 3-parameter model. The analysis involved 25 nucleotide sequences. Orange circles represent samples sequenced in this study

Fig. 5

Phylogenetic analysis based on the ITS2 spacer of the ribosomal RNA gene cluster of ticks. A phylogenetic tree based on ITS2 rDNA sequences. The tree was generated by the maximum likelihood method based on the Tamura 3-parameter model. The analysis involved 32 nucleotide sequences. Orange circles represent samples sequenced in this study