Rickettsia africae and Rickettsia massiliae in ixodid ticks infesting small ruminants in agro-pastoral settlements in Plateau State, Nigeria.

Arthropods, especially ixodid ticks, have been incriminated in the epidemiology of Spotted Fever Group rickettsioses globally leading to an increasing spectrum of emerging and re-emerging zoonoses with attendant consequences on trade and tourism. The objective of this study was to determine the role of ixodid ticks infesting small ruminants in Plateau State, Nigeria, in the epidemiology of Spotted Fever Group Rickettsiae (SFGR) in the study area. DNA from 130 out of 323 ixodid ticks collected from 179 goats and 121 sheep owned by agro-pastoralists in Plateau State were screened for the evidence of SFGR by molecular methods. Six tick species from four genera were identified: Amblyomma, Hyalomma, Rhipicephalus (Boophilus) and Rhipicephalus. Rhipicephalus sanguineus sensu lato (s.l.) was the predominant (54.5%) species among collected ticks. Tick infestation was significantly associated with the species of small ruminants, the sex of the animals and the sampling locations except for Jos South. Conventional PCR targeting the 381 bp of the citrate synthase (gltA) and 820 bp of the outer membrane protein B (ompB) genes detected DNA of SFGR in nine and eight samples, respectively. Sequence analysis revealed that five sequences obtained from Amblyomma variegatum were 99-100% identical to Rickettsia africae and three sequences from Rh. sanguineus (s.l.) were 100% identical to Rickettsia massiliae reported from Spain. To our knowledge, this is the first report of the detection of R. africae DNA in Am. variegatum collected from small ruminants in Plateau State. Ixodid ticks infesting small ruminants in Plateau state harbor DNA of SFGR with potential veterinary and public health implications.

Human follicular mites: Ectoparasites becoming symbionts.

Most humans carry mites in the hair follicles of their skin for their entire lives. Follicular mites are the only metazoans tha continuously live on humans. We propose that Demodex folliculorum (Acari) represents a transitional stage from a host-injuring obligate parasite to an obligate symbiont. Here, we describe the profound impact of this transition on the genome and physiology of the mite. Genome sequencing revealed that the permanent host association of D. folliculorum led to an extensive genome reduction through relaxed selection and genetic drift, resulting in the smallest number of protein-coding genes yet identified among panarthropods. Confocal microscopy revealed that this gene loss coincided with an extreme reduction in the number of cells. Single uninucleate muscle cells are sufficient to operate each of the three segments that form each walking leg. While it has been assumed that the reduction of the cell number in parasites starts early in development, we identified a greater total number of cells in the last developmental stage (nymph) than in the terminal adult stage, suggesting that reduction starts at the adult or ultimate stage of development. This is the first evolutionary step in an arthropod species adopting a reductive, parasitic or endosymbiotic lifestyle. Somatic nuclei show underreplication at the diploid stage. Novel eye structures or photoreceptors as well as a unique human host melatonin-guided day/night rhythm are proposed for the first time. The loss of DNA repair genes coupled with extreme endogamy might have set this mite species on an evolutionary dead-end trajectory.

Seroprevalence of Spotted Fever Group Rickettsiae in extensively managed sheep and goats in Nigeria, West Africa.

Sheep and goats raised extensively are frequently infested by Ixodid ticks that may act as vectors or reservoirs of Spotted Fever Group Rickettsiae (SFGR). A study to determine the seroprevalence of SFGR infection in 300 sheep and goats in Plateau State, Nigeria was conducted from September to November, 2018 using the Indirect Fluorescence Antibody Test (IFAT). Overall, 85 out of 300 animals (28.3%) were seropositive to SFGR. Relatively higher seroprevalence was recorded in sheep than goats (28.8% vs 28.0%) but the difference was not statistically significant (p > 0.05). Furthermore, seropositivity was not affected by age, sex or location of the animals screened in this study. This is the first serological study to report the prevalence of SFGR in sheep and goats using IFAT in this study area. The presence of SFGR antibodies in domestic ruminants is of public health concern considering the close association between farmers and their animals occasioned by the management system practiced in the study area. This finding calls for further studies to evaluate the level of human exposure to this group of pathogen.