Current distribution and disease association of Ixodidae (hard ticks) in Nigeria

Background: This review documents the hard tick species that have been reported in Nigeria, their distribution, pathogens transmitted and disease they cause in Nigeria; the literature review considered studies that were conducted between 2000 and 2021. Main body: The hard tick (Ixodidae) species widely present in the country are those of the genera; Amblyomma, Rhi-picephalus/Boophilus, Hyalomma, Ixodes, Dermacentor and Haemaphysalis among which, Amblyomma sp , Hyalomma sp and Rhipicephalus sp. were most widely reported. Ticks cause serious economic losses to the livestock industry via their negative impact on animal health in general and possible transmission of zoonotic pathogens by some species. Ticks’ distribution is favoured by factors which include uncontrolled cross-border movement of animals, lack of strict quarantine measures, extensive animal grazing and suitable climatic condition. Tick-borne diseases commonly reported included Babesiosis, Anaplasmosis, Theileriosis and Ehrlichiosis , while diseases such as Crimean-Congo Haemorrhagic Fever and Africa tick bite fever are under-reported. Also, there is paucity of information on the economic impact of these diseases. Measures that have been implemented in the control of ticks included the use of acaricides and to some extent vaccines. Conclusions: Ticks and tick-borne diseases constitute serious economic important and studies to fully ascertain these at the national level is recommended. Also, there is need for identification of other species of ticks and under-reported tick-borne diseases to develop more integrated control measures.


Background
Ticks are small arachnids belonging to the order Acarina, Suborder Ixodidae, family Ixodidae and Argasidae (Birara, 2017). In Africa, there was remarkable diversity in the tick fauna, with about 50 endemic tick species known to infest domestic animals, and the highest impact on livestock health caused by species belonging to only three genera, namely, Amblyomma, Hyalomma, and Rhipicephalus (Anna et al., 2012). Several studies in Nigeria have documented different species of ticks that infest cattle; however, with regard to the diseases, they cause more research to be focused. Also, the free crossborder movement of animals, especially cattle in West Africa with Nigeria as a case study, due to the ECOWAS protocol, leads to emergence of tick-borne diseases such as Crimea Congo Haemorrhagic fever, rift valley fever and ehrlichiosis among others which are under-reported. The aim of this review was to take a look at ticks' species in different geographical regions of Nigeria and the disease they transmit.
Ticks survived by feeding on the blood of mammals, birds, and sometimes reptiles and amphibians (haematophagy) and were vectors of a number of diseases that affect both humans and other animals (Biu et al., 2012;Cumming, 1998). These parasites constituted a major constrain to livestock production in Nigeria as they could cause considerable economic losses by affecting animal health and productivity (Anna et al., 2012;Fabiyi, 2007). The pathogenic effects of tick infestation were associated with their feeding pattern which is adapted for both penetrating the skin and transmitting microorganisms (Lysyk, 2013). The severe irritations caused by their bites, especially when numerous, could result in emaciation (deficiency in nutrients), anaemia, serious damage to hides and skin (skin lesions, impairment of animal growth) which are valuable export products in Nigeria (Fabiyi, 2007). Ticks were one of the major vectors transmitting pathogens responsible for babesiosis, theileriosis, anaplasmosis dermatophilosis, etc., to animals globally (Morel, 1989;Soulsby, 1982). Tick-borne diseases are of great economic importance due to losses they cause to the cattle industry globally. In Nigeria, the cattle industry contributes significantly to the economic wellbeing of the nomadic herd men as they rely on the income to sustain their families and the nation at large. The ECOWAS protocol allows for the free movement of people, goods and services across the West Africa region, and the porous nature of the borders allows this movement to go uncheck which pose risks in the spread of diseases. Nigeria shares border with Niger, Chad and Cameroon to North, and there is huge economic activity, especially as it relates to livestock with cattle dominating the markets. This forms the rationale behind this study in order to know the current state of tick-borne disease that has been reported and to see whether there is emerging treatment.

Tick-Borne Diseases
Tick-borne diseases are some of the major constraints to livestock health and production throughout Sub-Saharan Africa and in some cases affect humans (Jesca et al., 2014). The fact that ticks harbouring several pathogens, domestic and wild animals can become infected with these pathogens (Atsuwe et al., 2019). The disease transmitted by ticks are responsible for severe losses caused either by tick worry, blood loss, blood-related infections, damage to hides and udders and the transmission of toxins (Atsuwe et al., 2019;Pam et al., 2019). The major tickborne diseases that have been reported in Nigeria include Crimean-Congo Hemorrhagic, Babesiosis, Theileriosis, Anaplasmosis, ehrlichiosis (Babagana, 2019;Daniel et al., 2020;Hector et al., 2019).

Distribution of ixodid ticks in Nigeria
Ixodid ticks are widely distributed in Nigeria as shown by various studies across the country.
In Plateau State, the 3 ticks genera (i.e., Amblyomma, Hyalomma, and Rhipicephalus, including the Boophilus sub-genus) and 11 species ( (Lorusso et al., 2013). This study ascertained the presence of a broad variety of cattle tick species, most of which are of veterinary importance and the presence of each tick species was correlated with the potential occurrence of tick-borne pathogens and suggestions for tick control in the area were considered. In a study by Adang et al. (2015), the tick species of sheep and goats identified in Gombe State were Rhipicephalus species, Amblyomma species, Boophilus species, Ixodes ricinus and Hyalomma species. This study concluded that ectoparasites were common to both sheep and goats in Gombe State and thus could affect their health, productivity and economic value. Opara and Ezeh (2011) (Obadiah et al., 2017). In Sokoto State, the ticks identified in cattle were Rhipicephalus sanguineous,

Ixodid ticks in Nigeria and disease relation Babesiosis
Babesiosis is caused by microscopic parasites (intra erythrocytic protozoan parasites) that infect red blood cells, and different species of Babesia parasites were found in animals (domestic and wild) and a few in humans (Gad, 2019;Leeflang & Ilemobade, 1977). The disease is also referred to as piroplasmosis, cattle tick fever, or red water fever. Ticks such as Boophilus decoloratus, B. annulatus and B. geigyi were reported to transmit the parasite (Leeflang & Ilemobade, 1977). Although the major economic impact of babesiosis is on the cattle industry, infections in other domestic animals, including horses, sheep, goats, pigs, and dogs, assume varying degrees of importance throughout the world. Two important species in cattle B. bovis and B. bigemina are widespread in tropical and subtropical areas (Jemal, 2017). In a study conducted by Pukuma et al. (2011) on tick-borne infections of cattle, 3 species of tick-borne parasites encountered were Babesia bigemina, Theileria parva and Anaplasma marginale. Onoja et al. (2013) in a study reported cattle to be infected with Babesia bigemina. In a study to determine the prevalence of babesiosis in stable horses in Ibadan, Oyo State, Nigeria, 14.0% of local breed were positive for Babesia parasite at pre-polo competition phase, while 22.0% tested positive at the post-polo competition phase (Oladipo et al., 2015). This could have resulted from invasion of the polo club by ticks from the horses brought in for the competition. In sheep and goats, Babesia ovis was reported (Adamu & Balarabe, 2012).
Nonyelu (2013) reported Babesia species in dogs attending ECWA Veterinary Clinic, Bukuru, Jos, South Local Government Area, Plateau State. In Makurdi, Benue State, dogs were infected with Babesia canis and the ticks identified were Rhipicephalus, Boophilus and Amblyomma species (Omudu et al., 2007). Cletus (2019) in parasitological examination of 200 blood samples revealed that 23 were positive for Babesia canis; likewise, the dogs were infested with Rhipicephalus sanguineus. Konto et al. (2014) in a study found that 48 dogs were infected with Babesia canis out of a total of 400 and ticks such Boophilus spp, Rhipicephalus sanguineus, Hyalomma spp. and Amblyomma variegatum out of a total of 4216 tick species collected during the study. Isaac et al. (2020) in a study, found out that in blood samples of sheep and goat, Babesia spp. were reported to be present. A study carried out by Foluke et al. (2017) revealed that Babesia spp were present in 52 of the 109 blood samples of dogs. Obed and Imafidor (2018) reported that cattle examined were infected with Anaplasma spp., Theileria spp. and Babesia spp. from three  Philip et al. (2020) reported that from 300 blood samples of horses and using species-specificnested PCR-targeting genes for testing, 10 of samples were positive for Babesia caballi.

Anaplasmosis
In Nigeria, a survey on the prevalence of Babesiosis in Cattle and Goats at Zaria Abattoir by Onoja et al. (2013) revealed that out of 223 animals sampled at Zaria abattoir, 168 were cattle and 55 goats. Anaplasma marginale was found in cattle (58/168), and Anaplasma bovis was found in goats (25/55). Kamani et al. (2010) (2012) reported in a study "Prevalence of Haemoparasites of Sheep and Goats Slaughtered in Bauchi Abattoir" that blood samples collected from 200 animals 100 each of sheep and goats slaughtered at the abattoir were randomly sampled between July and December 2011, and the results showed that Anaplasma ovis was in sheep and in goat. Adejinmi et al. (2004), in "Studies on the blood parasites in West Africa Dwarf sheep in Ibadan, Nigeria" found that Anaplasma spp. were found in 24 out of a total of 214 blood samples collected. An overall prevalence of 33/200 of Anaplasma species was reported in cattle by Wada et al. (2020). In a study on haemoparasite of cattle, a prevalence of 18.5% of Anaplasma species was reported out of 162 blood samples collected (Sam-Wobo et al., 2016). Garba et al. (2011) revealed that 41 horses were positive for Theileria equi out of 51 horses examined. Anyanwu et al. (2016) reported Theileria spp. to be present in 7 out of 87 sheep sampled and 5 out of 178 goats sampled. Atsuwe et al. (2018) reported in a study that out of 228 cattle and dog each sampled, Theileria ovis (7.8%) was found to be present in goats. Qadeer et al. (2015) reported Theileria spp. 12 were found to be positive out of 100 blood samples collected. Vincenzo et al. (2016) reported that Theileria velifera and T. taurotragi. Kamani et al. (2010) found 21 blood samples were positive for Theileria mutans out of a total of 637 blood sampled tested. Adua and Idahor (2017) revealed that out of 34 blood samples of goats tested, 3 and 6 were positive for Theileria mutans and Theileria ovis, respectively. Turaki et al. (2014) revealed that out of 100 bloods sampled across three states in Nigeria, 94 were positive for Theileria equi. Philip et al. (2020) in a study revealed that Theileria equi (39) and Theileria haneyi (8) were present out of 300 blood samples of horses tested. Mohammed and Idoko (2012) reported Theileria ovis to be positive from 150 blood samples tested. Adamu and Balarabe (2012) in a study on haemoparasite of sheep and goats revealed that Theileria ovis was in blood samples of sheeps and in goat. The overall prevalence of Theileria spp in cattle slaughtered in Zango abattoir was 22/200 as reported by Wada et al. (2020). Anaplasma ovis was reported by Egbe-Nwiyi et al. (2017) in 23 blood samples of sheep and goats in Maiduguri abattoir. A study carried out on the molecular detection of Theileria species by Philip et al. (2020) reported that T. equi was prevalent in 39 of sampled blood and T. haneyi was prevalent in 8 of the blood samples out of a total of 300 blood samples of horses tested.

Rift Valley Fever (RVF)
On A cross-sectional study on the seropositivity of rift valley fever in pastoral cattle reported that out of 107 cattle breeds sampled an overall prevalence of 6 was reported ; similarly, in a separate study the authors also reported that out of 97 cattle tested 11 were found to be seropositive (Nma et al., 2018). Olaleye et al. (1996) reported that out of 2255 samples, 259 had haemagglutination-inhibiting and neutralizing antibodies in sheeps, goats, cattle, horses and camels. In a study "seroprevalence of rift valley fever virus infection among slaughtered ruminants in Jos, North-Central, Nigeria", Page 6 of 10 Kyari et al. The Journal of Basic and Applied Zoology (2022) 83:42 it was revealed that out of 100 blood samples collected from livestock cattle (50) and goat (50), 11 was positive for RVF in cattle 8 and in goats 3 were positive (Anejo-Okopi et al., 2020). In a study on one-humped camels in Northern Nigeria, Adamu et al. (2020) reported that an overall prevalence of 143, with older camels between the ages of 6-10 years having a prevalence of 77 out of a total of 720 blood samples tested.

Ehrlichiosis
Ehrlichiosis is an obligate intracellular tick-borne disease that infects different animal species; examples include Ehrlichia ruminantum in cattle, Erhlichia canis in dogs (Matur et al., 2019;Ogunkoya et al., 2011). Following PCR and reverse line blotting (RLB), 22 blood samples were reported to be positive for Ehrlichia or Anaplasma spp. (Vincenzo et al., 2016). Similarly, PCR and RLB revealed that out of 100 blood samples collected, 5 with either Ehrlichia canis or Anaplasma sp. (Mathew et al., 2014). Matur et al. (2019) in a study using thin blood smear revealed that out of 282 blood samples collected from dogs, 40 were positive for Erhlichia canis. Ehrlichia ewingii and Ehrlichia chaffeensis were detected in a single tick only Anna et al. (2012). There is, however, paucity of information with regard to other forms of Erhlichiosis spp. (Table 2).

Economic importance
The economic losses due to Babesiosis, Anaplasmosis and Theileriosis have been divided into direct and indirect. The direct production losses are those that are directly attributable to presence of disease in animal population through morbidity and mortality (Jemal, 2017;Latif & Walker, 2016). Other losses are related to the animals that recovered that may suffer from weight loss, lesions such as soft and pulpy spleen, damage and irritation to hide, swollen liver, dark-coloured kidneys, anaemia and jaundice, produce low milk yields, reduction in meat, provide less draught power, and suffer from reduced fertility and delays in reaching maturity (Haranahalli et al., 2014;Jemal, 2017).

Possible factors influencing tick distribution
Animal movement from one ecological zone to another is widely considered as means of introduction of ticks into new ecosystems; the tribes associated with this movement are mostly the Fulani's, and there is also the movement of animals in the wild which can also contribute to distribution (Hassan & Salih, 2013;Ikpeze et al., 2011). Climate change such as desertification, drought, increase or decrease in rainfall and human activities such as deforestation and establishment of large-scale agriculture schemes affect habitats of ticks and hence their existence or non-existence (Hassan & Salih, 2013). Environment characterized by low rain fall is dangerous for tick survival, especially larval stages as they are susceptible to drying out; however, species with seasonal life cycle stand a chance of surviving (Ikpeze et al., 2015). The high infection rate among different animal species could be attributed to their life cycle as some tick species are host specific and free ranging among animals as they cover long distance grazing and crisscrossing vector infested areas and thus bring them in contact with the tick vector, whereas the low infection rate could be attributed to the fact some animals are usually kept in pens which restrict their level of exposure to tick infestation (Pukuma et al., 2011).

Control of ticks and treatment of tick-borne diseases
The economic cost in the control of ticks and tick-borne diseases has to do with the use of acaricides and vaccines; however, there has been emergence of resistant strains of ticks, limitations to the use of chemicals as some might be detrimental to human health (Yakubu et al., 2015). Several concepts such as integrated tick control strategies (host resistance to ticks and diseases they transmit), use of biological control measures, cross-breeding, and the development of vaccines against tick antigen have been deployed in the control of ticks (Jonson & Piper, 2007). Environmental management such as seasonal dynamics of tick infestation and extensive system of raising animals when compared to intensive system increases the risk of tick infestation (Jonson & Piper, 2007. The most conventional means used in the control of ticks is dipping or spraying with chemicals (Jongejan & Uilenberg, 1994). Commercial Acaricides such as Formamidine, Phenylpyrazole, Synthetic pyrethroids and Macrocyclic lactone were used in an in vitro study against adult Rhipicephalus (B.) annulatus, and the Lethal Concentration (LC 50 ) for each was found to be 100, 8000, 2300 and 6000 ppm, respectively (Foluke et al., 2020). In a study on the efficacy of three organophosphates (Chlorfenvinphos, Diazinon and Coumaphos) on different stages of development of Amblyomma variegatum, chlorfenvinphos caused the highest mortality rate against all stages of development of the tick specie, while diazinon was the least effective (Natala et al., 2012). Breed of cattle such as Zebu (Bos indicus) has been reported to be more resistant to ticks than Bos indicus and Bos taurus crosses; cross-breeding these cattle with other breeds could lead to a more resistant breed (Musa et al., 2014;Yakubu et al., 2015). Vaccines have been in use in the treatment of tickborne diseases such as anaplasmosis, babesiosis among other; strains of Babesia bovis and Babesia bigenia which are more virulent in nature than strain of Anaplasma marginale have been used to reduce their virulence. They have been developed in Australia and exported to other countries; there is, however, paucity of information on use of vaccines in Nigeria (Dadson, 1991).

Conclusions
This review shows that tick species of the genera Amblyomma, Rhipicephalus/Boophilus, Hyalomma, Ixodes, Dermacentor and Haemaphysalis have been reported to be widely distributed in Nigeria. The availability of suitable host, movement of animals from one region of the country to another and favourable climatic conditions are responsible for the spread. Despite paucity of information with regard to the economic cost associated with losses to the livestock industry as a result of ticks and tick-borne diseases, this ectoparasites and the pathogens they transmit are of veterinary and public health concern.
Research should be carried out especially as it concerns tick-borne diseases such as Crimean-Congo haemorrhagic fever and Africa tick bite fever among others of public health importance in the country due to lack of documented information. Local development of vaccines should be encouraged through research. Herders should be educated and encouraged to go into ranching in other to reduce cross-border movement of animals which plays a role in the introduction of new species.