Rhipicephalus species are distributed globally with a notifiable presence in Southeast Asia (SEA) within animal and human populations. The Rhipicephalus species are highly adaptive and have established successful coexistence within human dwellings and are known to be active all year round, predominantly in tropical and subtropical climates existing in SEA.
The host specificity of Rhipicephalus in SEA can be narrowed down based on previous incidences and findings. They are mainly associated with several types of livestock and companion animals (Table 1).
Host Type |
---|
Country |
---|
Tick Species |
---|
Host |
---|
Reference |
---|
Livestock | Cambodia | Rhipicephalus microplus | Unknown | [22] |
Rhipicephalus australis | Unknown | [42] | ||
Indonesia | Rhipicephalus australis | Unknown | [42] | |
Rhipicephalus haemaphysaloides | Bos taurus Bubalus bubalis Capra aegagrus hircus |
[43] | ||
Rhipicephalus microplus | Bos taurus Bubalus bubalis Capra aegagrus hircus Equus caballus Sus scrofa |
[30][43][44] | ||
Rhipicephalus pilans | Bos taurus Bubalus bubalis Capra aegagrus hircus Equus caballus Ovis aries |
[30][43][44] | ||
Rhipicephalus sanguineus s.l. | Bos taurus Bubalus bubalis Gallus gallus domesticus Sus scrofa domesticus |
[44] | ||
Rhipicephalus haemaphysaloides | Bos sp. | [23] | ||
Laos | Rhipicephalus microplus | Bos sp. | [23] | |
Rhipicephalus australis | Unknown | [42] | ||
Malaysia | Rhipicephalus microplus | Bos taurus | [18][45] | |
Rhipicephalus microplus | Bos sp. | [19] | ||
Myanmar | Rhipicephalus microplus | Bos sp. Sus scrofa |
[46] | |
Singapore | Rhipicephalus microplus | Bos sp. and Bos taurus | [27][47][48] | |
Thailand | Rhipicephalus australis | Unknown | [42] | |
The Philippines | Rhipicephalus microplus | Bos sp. and Bos indicus Bubalus bubalis Capra aegagrus hircus |
[28][29][49] | |
Rhipicephalus haemaphysaloides | Bos sp. | [50] | ||
Timor-Leste | Rhipicephalus microplus | Bos sp. Capra aegagrus hircus |
[50] | |
Rhipicephalus sanguineus s.l. | Bos taurus | [50] | ||
Rhipicephalus annulatus | Bos sp. | [51] | ||
Vietnam | Rhipicephalus microplus | Bos sp. | [24] | |
Rhipicephalus sanguineus s.l. | Bos sp. | [52] | ||
Rhipicephalus haemaphysaloides | Canis lupus familiaris | [43] | ||
Companion animals | Indonesia | Rhipicephalus sanguineus s.l. | Canis lupus familiaris Felis catus |
[53][43][54] |
Rhipicephalus haemaphysaloides | Canis lupus familiaris | [23] | ||
Laos | Rhipicephalus sanguineus s.l. | Canis lupus familiaris | [33][55] | |
Rhipicephalus sanguineus s.l. | Canis lupus familiaris | [37][56][57][58][59][60][61][62] | ||
Malaysia | Rhipicephalus sanguineus s.l. | Canis lupus familiaris | [34] | |
Myanmar | Rhipicephalus sanguineus s.l. | Canis lupus familiaris Felis catus |
[53][62][63] | |
Singapore | Rhipicephalus sanguineus s.l. | Canis lupus familiaris | [21][36][62] | |
Thailand | Rhipicephalus sanguineus s.l. | Canis lupus familiaris Felis catus |
[53][29][62] | |
The Philippines | Rhipicephalus haemaphysaloides | Canis lupus familiaris | [52] | |
Vietnam | Rhipicephalus sanguineus s.l. | Canis lupus familiaris | [21][35][52][62] | |
Rhipicephalus haemaphysaloides | Forest rats * | [43] | ||
Rodents | Indonesia | Rhipicephalus microplus | Rattus exulans Rattus hoffmanni Rattus rattus |
[44] |
Rhipicephalus pilans | Niviventer fulvescens Rattus argentiventer Rattus exulans Rattus rattus Rattus tiomanicus |
[43][44][64] | ||
Rhipicephalus sp. | Sundamys muelleri | [65] | ||
Malaysia | Rhipicephalus haemaphysaloides | Pteropus vampirus Rusa unicolor Helarctos malayanus Panthera tigris Varanus salvator Sus scrofa Hylomys suillus |
[43][66] | |
Wild animals | Indonesia | Rhipicephalus microplus | Bos javanicus Manis javanica Rusa timorensis Rusa unicolor |
[43][44] |
Rhipicephalus pilans | Crocidura nigripes Hylomys suillus Rusa timorensis Suncus murinus Sus scrofa |
[43][67] | ||
Rhipicephalus sanguineus s.l. | Bos javanicus Rusa unicolor |
[43] | ||
Rhipicephalus haemaphysaloides | Arctictis binturong Cuon alpinus Martes flavigula Neofelis nebulosi |
[68] | ||
Thailand | Rhipicephalus microplus | - | [44] | |
Human | Indonesia | Rhipicephalus pilans | - | [44][64] |
Rhipicephalus sanguineus s.l. | - | [43] | ||
Rhipicephalus microplus | - | [68] | ||
Thailand | Rhipicephalus sanguineus s.l. | - | [69] |
Tick-borne diseases transmitted by Rhipicephalus ticks affect cattle production worldwide, including SEA countries [70][71][72]. Studies have shown the potentially devastating impact of R. microplus infestation on developing countries’ livestock economies [31]. These losses are bothered by developing countries’ inability to control and monitor the diseases; hence, it impairs the livestock economy [73]. The distribution and prevalence of these diseases across the SEA geopolitical area appear to be quite eco-oriented. Important Rhipicephalus-borne diseases in SEA are babesiosis, anaplasmosis, theileriosis, and ehrlichiosis. Some other pathogens transmitted by R. sanguineus s.l. include HepatozoonHepatozoon canis canis [39][60][74] and CoxiellaCoxiella burnetti burnetti [59], which causes hepatozoonosis and Q-fever, respectively. The host range for these diseases is reasonably consistent, although outliers to the known host range for some tick-borne diseases have also been reported in the SEA. For instance, rare infections in a previously unknown host for BabesiaBabesia canis, canis, such as in wild rodents, have been reported [75] in Thailand. Similarly, Lim et al. [76] reported a rare occurrence of human babesiosis (caused by BabesiaBabesia microti) microti) exported from the USA into Singapore.
Babesiosis affects most warm-blooded animals with high economic and health consequences. Babesia caballi and Theileria equi collectively cause equine piroplasmosis characterized by fever and jaundice, mainly in horses and other Equidae in SEA [77][78]. Anaplasma that causes anaplasmosis is a tropical to subtropical rickettsial disease of ruminants and companion animals. AnaplasmaAnaplasma marginale marginale annd A. centrale are the notable species in cattle and buffaloes across SEA [79], while A. platys occur in dogs [74][80].
Currently, tick-borne protozoal and rickettsial diseases are invariably endemic in SEA. Concurrent infectious diseases with Babesia, Theileria, Anaplasma and Ehrlichia Ehrlichia spp.spp. are increasingly reported. The theory of increasing sensitivity of pathogens detection with the help of molecular work could logically fit this scenario. However, it remains unclear why such co-morbidities are consistently challenging to treat, and the ticks are difficult to control in the environment. Hence, an elaborate effort is required to identify the epidemiological patterns of Rhipicephalus, the pathogens they transmitted and the rising incidence of resistance to control drugs of this tick in SEA. Molecular detection of the presence of pathogens in squashed ticks is more direct in understanding the host-parasite dynamics for TBDs should be extended further to involve more host species of Rhipicephalus in the region. It remains crucial to determine the extent to which Rhipicephalus species act as biological, mechanical vectors or both for pathogens of interest.
Tick-borne protozoan diseases cause substantial economic loss in Thailand’s dairy and beef industries [81]. High mortality rates were noticed in the 50 million USD imported exotic breed of cattle due to tick-borne diseases. The Department also expended over 20 million USD to diagnose, treat and control diseases of animals. However, the exact economic impacts of ticks and tick-borne diseases in SEA are not available due to the lack of farm economic impact study compared to the European and African regions [82].
The complex interaction, mainly due to the host’s diverse immune mechanisms and non-immune structural components, has contributed to various responses towards tick feeding [83]. Most mammals mount an immunological response to a feeding tick bite. It is often more vital to the host’s species with little or no evolutionary experience. Some species or breed appear to be better adapted to the tick bite; for instance, BosBos indicus indicus cattle breeds are more resistant to R. microplus than B. taurus breeds, although considerable variation in resistance exists between and within breeds [84]. The pattern of host resistance to ticks in the SEA region is not necessarily different from other parts of the world. Such resistance is often dependent on the commonality of the several species. Resistance is generally believed to be under genetic control [85]; thus, highly resistant animals can be selected to progress genetic improvement in tick resistance within a herd.
Overall, resistance to R. microplus infestation in cattle has many effector mechanisms. Although some of the mechanisms and modulating factors have been identified and quantified, much remains to be explained. Studying the genetic resistance to ticks among different breeds of cattle can contribute to alternative control methods. Investigations have intensified the crossing of these two groups, aiming to obtain more resistant animals to the conditions found in tropical countries and are also good meat producers. Regarding SEA, in addition, the host-range resistant factors should be expanded to include companion animals, wild animals, and livestock to understand the phenomenon. For future research, potential research of wild cattle in SEA such as Banteng (Bos javanicus), Gaur (Bos gaurus) and water buffalo (Bubalus bubalis) can be explored for conservation and genetic diversification purposes.
Rhipicephalus ticks’ control mainly depends on conventional acaricides. However, the exhaustive use of these chemicals has resulted in tick populations developing resistance to major acaricide chemical classes [86]. Ivermectin, a macrocyclic lactone, is used as an endo-ectoparasiticide. It is used as an acaricide and anthelmintic in goat and sheep farms in Malaysia [87], Indonesia [88], and Thailand [89]. Although there is currently no report of acaricide-resistant Rhipicephalus ticks in the SEA region, we cannot discount the possibility of this event. Thus, the application of alternative tick control approaches, including the rotation of acaricide, sterile hybrid ticks, pasture rotation, anti-tick vaccine, development of host resistance to ticks and the use of plant extracts, should be explored in SEA.
The alternation of the use of two or more acaricide with different modes of action could be an advantageous tick control method as well as a measure to prevent cross-resistance [86].
The success of mosquito control using genetic control methods [90] rekindled interest in using this method to control Rhipicephalus ticks. Osburn and Knipling [91] demonstrated sterile males’ production and fertile females through the mating between R.R. annulatus annulatus and R.R. microplus. microplus. The backcrossing of fertile female progenies also produces sterile males and fertile females [91].
The per capita consumption of livestock products among SEA countries is projected to increase in the years to come [92] significantly. The increase in demand for livestock products has intensified the race to acquire agricultural land between the livestock and crop farmers. Integrating both cash crop plantations with ruminant cultivation is very much encouraged [93].
Since the excessive use of acaricides has been shown to cause the accumulation of chemical residues in milk, meat, and the environment, safer methods have arisen. Vaccination or immunological control is touted as the most promising, environmentally friendly, and sustainable strategy for the management of Rhipicephalus infestation [94].
Plant extracts or secondary metabolites, including flavonoids, terpenes, spilanthol and coumarins, have been studied comprehensively for their potential to control ticks [95].
In essence, livestock farmers in SEA are the most burdened by problems associated with R.R. microplus microplus infestation. However, due to the structural issues plaguing the SEA livestock industry (such as the high cost of animal feeds, lack of quality breeds, inefficient coordination of agricultural policies and limited industry linkages [96][97][98][99], most smallholder farmers resort to using acaricide as it is the most cost-effective method to control tick infestation. Hence, in addition to structural reforms to the agriculture policies by the respective governments, farmers must be educated on sustainable agricultural practices and shown the impact of such practices in improving income levels [100]. Besides, there should be more university-industry-farm partnerships for the pilot-testing of newer technologies such as the application of Internet-of-Things and artificial intelligence to improve aspects of livestock farming [96].