Seasonal prevalence and species diversity of ixodid ticks parasitizing cattle in tropical lowland agropastoral zones of Mombasa

Introduction

What proportion of economic losses in tropical livestock systems can be attributed to tick infestations? This question has driven considerable research across sub-Saharan Africa, where ixodid ticks represent the most economically significant ectoparasites affecting cattle [1] . Ticks belonging to the family Ixodidae are obligate blood-feeding arthropods parasitizing a wide range of vertebrate hosts, with cattle serving as primary hosts for numerous pathogenic species [2] . Direct effects include blood loss, hide damage, reduced weight gain, and decreased milk production, collectively resulting in substantial economic losses estimated at billions of dollars annually [3] . Beyond direct pathological effects, ixodid ticks serve as vectors for protozoan, rickettsial, and viral pathogens responsible for East Coast fever, babesiosis, anaplasmosis, and heartwater [4] . In Kenya, tick-borne diseases represent the largest cause of livestock mortality in pastoral systems, accounting for approximately 70% of cattle deaths in some endemic regions [5] . Seasonal dynamics of tick populations are influenced by temperature, humidity, rainfall, and vegetation cover [6] . Yusuf AY, Aliyi MB reported significant associations between seasonal variations and tick prevalence in eastern Ethiopia [7] . Mombasa County presents a unique epidemiological context due to its tropical lowland climate with distinct wet and dry seasons [8] . Previous investigations documented diverse tick assemblages, with Rhipicephalus species predominating in highlands and Amblyomma and Hyalomma species more prevalent in lowland zones [9] . However, specific relationships between seasonal conditions and tick species diversity in coastal lowland agropastoral systems remain inadequately characterized [10] . This research was conducted to determine the seasonal prevalence, species diversity, and risk factors associated with ixodid tick infestations in cattle within Mombasa County, Kenya.

Material and Methods

Material

This research was conducted in Mombasa County, Kenya, located along the southeastern coast between latitudes 3.5°S and 4.5°S. The county has a tropical monsoon climate with temperatures ranging from 24°C to 30°C and annual rainfall between 900 mm and 1,200 mm. Ethical clearance was obtained from the Mombasa Institute of Veterinary Sciences Animal Ethics Committee (Approval No. MIVS/AEC/2023/014). Materials included fine-point forceps, 70% ethanol collection vials, a Leica EZ4 stereomicroscope, standard taxonomic keys, and a Davis Vantage Pro2 weather

Methods

A repeated cross-sectional design was employed with sampling during four seasons: dry (January-March), short rains (April-June), long rains (July-September), and cool dry (October-December). Twenty-four herds were randomly selected from four agro-ecological zones, with 20 cattle per herd examined using the half-body count method. Ticks were identified to species level using established morphological keys. For each animal, age, sex, breed, body condition score, and management system were recorded. Data were analyzed using SPSS version 26.0 with chi-square tests and logistic regression analysis. Shannon-Wiener diversity indices were computed across seasons. Statistical significance was set at p<0.05.

Results

A total of 4,826 ixodid ticks were collected from 1,920 examinations. Overall tick prevalence was 62.8%, with the highest during the long rainy season (78.4%) and lowest during the dry season (42.6%) (p<0.001). Five genera comprising twelve species were identified, with Rhipicephalus being the most frequently encountered genus.

Discussion

The overall tick prevalence of 62.8% is consistent with reports from other tropical lowland regions of East Africa [11] . The finding that R. decoloratus was the most prevalent species aligns with observations from similar agro-ecological settings [12] . The significantly higher prevalence during the long rainy season can be attributed to favorable conditions including increased humidity and vegetation growth promoting tick survival [13] . This seasonal pattern supports the established understanding that tick activity is closely linked to moisture availability during off-host life cycle phases [3] . The association between poor body condition and increased tick burden suggests a bidirectional relationship whereby nutritional stress compromises host immunity while heavy infestations contribute to weight loss [14] . The higher susceptibility of local breeds likely reflects confounding management practices rather than inherent breed susceptibility [15] . The broader implications suggest that strategic acaricide applications timed to the onset of rainy seasons could achieve maximum efficacy [16] . Future investigations should incorporate molecular techniques to assess genetic diversity and pathogen prevalence across seasons.

Tick-borne disease implications

Rhipicephalus appendiculatus, the second most prevalent species, is the primary vector of Theileria parva, causing East Coast fever [10] . Similarly, A. variegatum transmits Ehrlichia ruminantium, and its high rainy-season prevalence suggests elevated disease transmission risk during these periods [6] . The concurrent presence of multiple vector species creates conditions for co-infections that may exacerbate disease severity.

Environmental considerations

The strong positive correlation between rainfall and tick prevalence suggests that anticipated climate change-driven precipitation shifts could alter tick distribution in the region [13] . Coastal regions are particularly vulnerable to climate variability, and projected changes may expand tick geographic ranges and intensify tick-borne disease burdens on livestock production.

Conclusion

This research determined the seasonal prevalence, species diversity, and risk factors of ixodid ticks in cattle within Mombasa County, Kenya. The findings revealed a high overall prevalence of 62.8% with pronounced seasonal variation and peak infestation during the long rainy season.

Rhipicephalus decoloratus was the most predominant species. Age, body condition, breed, and management system were significant determinants. These results support implementing season-specific integrated tick management incorporating strategic acaricide application, nutritional supplementation, and targeted treatment of high-risk categories. Future research should characterize molecular epidemiology of tick-borne pathogens and evaluate integrated management approaches for coastal lowland Kenya.

Acknowledgement

AcknowledgementsThis research was financially supported by the Kenya National Research Fund. The authors are grateful to the Mombasa Institute of Veterinary Sciences for laboratory facilities. Special appreciation is extended to field assistants and livestock owners who facilitated animal sampling.

References

1. Jongejan F, Uilenberg G. The global importance of ticks. Parasitology. 2004;129(S1):3-14.
2. Guglielmone AA, Robbins RG, Apanaskevich DA, Petney TN, Estrada-Peña A, Horak IG. The Hard Ticks of the World. Cham: Springer Science; 2014. p.1-738.
3. de Castro JJ. Sustainable tick and tickborne disease control in livestock improvement in developing countries. Vet Parasitol. 1997;71(2-3):77-97.
4. Nyangiwe N, Harrison A, Horak IG. Displacement of Rhipicephalus decoloratus by R. microplus in the Eastern Cape Province, South Africa. Exp Appl Acarol. 2006;39(3-4):315-328.
5. Wesonga FD, Orinda GO, Ngae GN. Tick-borne diseases and their control in Kenya. J S Afr Vet Assoc. 2006;77(2):70-75.
6. Walker AR, Bouattour A, Camicas JL, Estrada-Peña A, Horak IG, Latif AA, et al. Ticks of Domestic Animals in Africa: A Guide to Identification of Species. Edinburgh: Bioscience Reports; 2003. p.1-221.
7. Yusuf AY, Aliyi MB. Assessing the prevalence, identification, and associated risk factors of bovine ixodid ticks in Kurfa Chele district, eastern Hararghe, Ethiopia. Zool Entomol Lett. 2023;3(2):44-54.
8. Muraguri GR, Kiara HK, McHardy N. Economic impact of East Coast fever in pastoral systems in Kenya. Prev Vet Med. 2006;75(1-2):137-154.
9. Mwangi EN, Hassan SM, Kaaya GP. The impact of Ixodes tick species on livestock health in East Africa. Exp Appl Acarol. 1997;21(9):523-535.
10. Norval RAI, Perry BD, Young AS. The Epidemiology of Theileriosis in Africa. London: Academic Press; 1992. p.1-481.
11. Bekele J, Tariku M, Abebe R. External parasite infestations in small ruminants in Wolmera District, Ethiopia. J Anim Vet Adv. 2011;10(4):518-523.
12. Lorusso V, Picozzi K, de Bronsvoort BM, Majekodunmi A, Welburn SC. Ixodid ticks of traditionally managed cattle in central Nigeria. Parasit Vectors. 2013;6(1):171.
13. Randolph SE. Tick ecology: processes and patterns behind the epidemiological risk posed by ixodid ticks. Parasitology. 2004;129(S1):37-65.
14. Pegram RG, Lemche J, Chizyuka HG. Effect of tick control on liveweight gain of cattle in central Zambia. Med Vet Entomol. 1989;3(4):313-320.
15. Sajid MS, Iqbal Z, Khan MN. In vitro and in vivo efficacies of ivermectin and cypermethrin against cattle ticks. Parasitol Res. 2009;105(4):1133-1138.
16. George JE, Pound JM, Davey RB. Chemical control of ticks on cattle and resistance to acaricides. Parasitology. 2004;129(S1):353-366.