The comparative prevalence of five ixodid tick species infesting cattle and goats in Maputo Province , Mozambique

DE MATOS, C., SITOE, C., NEVES, L., NÖTHLING, J.O. & HORAK, I.G. 2009. The comparative prevalence of five ixodid tick species infesting cattle and goats in Maputo Province, Mozambique. Onderstepoort Journal of Veterinary Research, 76:201–208 This study compares the prevalence of ixodid tick species on cattle and goats in Maputo Province. Adult ticks as well as the nymphs of three species, and only the adults of two species were collected from sets of five cattle at 21 localities throughout the province and compared with those collected from similar sets of goats at the same places. Amblyomma hebraeum adults and/or nymphs were present on cattle and on goats at all 21 localities, and 90 cattle and 22 goats were infested with adult ticks. Rhipicephalus (Boophilus) microplus adults and/or nymphs were collected from cattle at 20 and from goats at 15 localities, and 92 cattle and 34 goats were infested [Chi-square test (2), P < 0.001]. The total length of several maturing female R. (Boophilus) microplus collected from cattle and goats exceeded 5 mm, indicating that they successfully engorge on both host species. Rhipicephalus appendiculatus adults and/or nymphs were present on cattle at 15 and on goats at 13 localities, but 28 cattle and only one goat were infested with adult ticks (2, P < 0.001). Adult Rhipicephalus evertsi evertsi were recovered from cattle at 20 and from goats at 17 localities, and 74 cattle and 69 goats were infested. Adult Rhipicephalus simus were collected from cattle at 18 and from goats at 11 localities (Fisher’s exact test, P = 0.04), and 60 cattle and 14 goats were infested (2, P < 0.001). These findings underscore the advisability of including goats in acaricide application programmes designed for the control of tick-borne diseases in cattle at the same locality.

In KwaZulu-Natal Province, South Africa, Baker & Ducasse (1968) examined cattle at five localities at which goats were also present, and in the Eastern Cape Province Nyangiwe & Horak (2007) examined sets of five cattle and five goats at 72 communal cattle dip-tanks.The latter authors stated that there are no tick species that infest either of these hosts to the exclusion of the other in that region of the country.However, whereas cattle may harbour large numbers of both adult and immature ticks (Baker & Ducasse 1967), goats are often hosts of large numbers of immature ticks and fewer adults (Baker & Ducasse 1968;MacIvor & Horak 2003).Baker & Ducasse (1968) and Nyangiwe & Horak (2007) concluded that goats play an important role in maintaining infestations of ticks that normally infest cattle, and recommended that they should be included in tick control programmes designed for cattle on the same properties.
The objective of the present study was to compare the prevalence of infestation of the major ixodid tick species that infest sympatric cattle and goats in Maputo Province, Mozambique.

Localities and animals
Thirty localities spread throughout Maputo Province were visually selected from a map of the province.Ticks were collected from cattle at each of these localities, and from goats at 25.However, the required numbers of five animals of both species were realized at only 21 of these sites, and consequently only the tick burdens of animals examined at the latter localities were compared for the purpose of this communication.The 21 localities at which ticks were collected are plotted in Fig. 1.It is most unlikely that cattle or goats at any of these localities had been treated with an acaricide during the 12 months preceding tick collection.

Tick collections
Ticks were collected from the ears, bodies, bellies, feet, tails and peri-anal regions of the cattle and goats on the single occasion that each locality was visited.The collections of ticks from each bovine or goat were not intended to be exhaustive, and focused on adult ticks, but several nymphs of A.

Presentation of data
The chief comparison made was between the presence of adult ticks of four of the major tick species, namely A. hebraeum, R. appendiculatus, R. e. evert si and R. simus on cattle and goats.However, because large numbers of nymphs of both A. hebraeum and R. appendiculatus were also incidentally collected their presence on cattle and goats was also separately compared.The fifth major tick species, R. (B.) microplus, is a one-host tick, with all stages of development present on the host at the same time.The adults and nymphs of this species were thus considered an entity and their presence was compared as such on the cattle and goats.
Because the collections of ticks from each animal were not complete, the actual numbers of ticks recovered from the cattle and goats cannot be compared.However, the presence or absence of a par-ticular tick species on the two hosts, as well as at the various sampling localities, can be compared.These data are presented in tabular format together with similar data collected from cattle and goats in the Eastern Cape Province, South Africa.
The proportion of infested cattle pooled from all sampling sites was compared by means of a Chisquare ( 2 ) test to the proportion of infested goats pooled from the same sampling sites.The proportion of localities at which infested cattle were present was compared to the proportion at which there were infested goats by means of Fisher's exact test.
A paired t-test was used to compare the differences between the average numbers of infested cattle and infested goats at each dip-tank.If the differences were not normally distributed Wilcoxon's signedrank test was used.The NCSS 2004 software package (www.NCSS.com)was used for all statistical analyses.The data are also presented graphically.
The proportion and average numbers of cattle infested with R. (Boophilus) microplus were significantly greater than the proportion and average numbers of infested goats ( 2 , P < 0.001, and paired t-test, P < 0.001, respectively).There was, however, no difference in the proportion of localities at which infested cattle and goats were present (Fisher's exact test, P = 0.18) (Table 1).
A total of 4 932 R. (B.) microplus was collected from the cattle compared to a total of 357 ticks from the goats (Table 2).Not all female R. (B.) microplus collected were available for measurement, but 33.9 % (151) out of a total of 445 female R. (B.) microplus collected from some of the cattle exceeded 5 mm in length, while 20.3 % (15) of a total of 74 females collected from some of the goats also exceeded this length.
Compared to goats, the proportion of cattle and the average numbers infested with adult R. appendiculatus at each locality were significantly greater ( 2 , P < 0.001, Wilcoxon signed-rank test, P < 0.01 respectively) (Table 1).The proportion of cattle infested with nymphs and adults was also significantly greater than the proportion of goats similarly infested ( 2 , P = 0.02).The average numbers of cattle and goats that were infested with R. appendiculatus nymphs and/or adults at each locality, and the proportion of localities at which infested cattle and goats were present did not differ significantly (paired t-test, P = 0.07, and Fisher's exact test, P = 0.74, respectively).
Few R. evertsi evertsi nymphs, but several hundred adults were collected from both cattle and goats.The proportions and average numbers of cattle and goats that were infested with adult ticks, and the proportion of localities at which infested cattle and goats were present were similar ( 2 , P = 0.46, paired t-test, P = 0.5, and Fisher's exact test, P = 0.34, respectively) (Table 1, Fig. 2).Only adult R. simus were collected from the cattle and goats.A significantly greater proportion of cattle than goats was infested ( 2 , P < 0.001), and infested cattle were present at a significantly greater proportion of localities than infested goats (Fisher's exact test, P = 0.04) (Fig. 2).The average number of infested cattle at each locality was also significantly greater than the average number of infested goats (Wilcoxon signed-rank test, P < 0.001) (Table 1).2).Although the proportion of goats infested with adult ticks in the current survey was reasonably similar to that conducted by Nyangiwe & Horak (2007), 20.9 % compared to 16.9 %, the proportion of infested cattle differed considerably, 85.7 % compared to 38.3 % (Table 2).Horak, Mac-Ivor, Petney & De Vos (1987) concluded that the larger the host species the greater the likelihood that it would harbour adult A. hebraeum, and this was confirmed by the present findings.
Amblyomma hebraeum was present at every locality sampled in Maputo Province (Fig. 1), compared to only 54.2 % of 72 localities in the Eastern Cape Province (Nyangiwe & Horak 2007).This difference can probably be ascribed to the prevailing climate of Maputo Province as being more suitable for A. hebraeum than that of the eastern regions of the Eastern Cape Province.
Amblyomma hebraeum is the most important southern African vector of Ehrlichia ruminantium, the causative organism of heartwater in domestic and some wild ruminants (Norvall & Horak 2004).Goats are particularly susceptible, and according to Allsopp, Bezuidenhout & Prozesky ( 2004) up to 30 % of goats in some parts of the rural farming areas of South Africa become infected annually.Whereas, in the absence of challenge, immunity in cattle lasts for approximately 2 years after immunization, immunity in goats is extremely variable (Allsopp et al. 2004).
Rhipicephalus (Boophilus) microplus is a one-host tick that infests cattle, and is usually only found on other animals provided infested cattle are present at the same locality.As far back as 1943, Theiler, in her monograph on the ticks of domestic livestock in Mozambique, mentioned that the tick that she then referred to as Boophilus (Uroboophilus) fallax, and that is now accepted as R. (B.) microplus (Camicas et al. 1998), was found mostly on cattle, but that it could also occur on equines, ovines and caprines (Theiler 1943).Furthermore Dias (1991) 2).They also noted that a large proportion of maturing female ticks collected from goats were 5 mm or more in length (standard females), indicating that they should complete their engorgement and detach within the following 24 h.Considering that this is a one-host species it is only necessary to show that engorged female ticks that detach from goats can lay fertile eggs to prove that R. (B.) microplus can complete its entire life cycle on these animals.
The recovery of R. (B.) microplus from goats at so many localities in the present study can partly be ascribed to the high prevalence of infestation on cattle at the same localities (Fig. 2).The presence of standard female ticks on many of the goats in this survey as well as that of Nyangiwe & Horak (2007) is a fair indication that in at least two regions of southern Africa R. (B.) microplus has adapted to feeding on goats, and may even be able to survive on these animals in the complete absence of cattle.Nyangiwe & Horak (2007) 2007).These animals as well as many smaller domestic and wild herbivores can also all be heavily infested with the immature stages of this tick (Baker & Ducasse, 1967, 1968;Horak, Gallivan, Braack, Boom ker & De Vos 2003;Horak et al. 2007).Contrary to the study of Baker & Ducasse (1968) in KwaZulu-Natal, in which slightly more adult R. appendiculatus were collected from cattle than from goats, and that of Nyangiwe & Horak (2007) in the Eastern Cape Province, in which slightly more goats than cattle were infested with adult ticks, only three adult ticks were recovered from a single goat in the present survey compared to 269 adult ticks from 28 cattle (Table 2, Fig. 2).One of the reasons for this anomaly can be that the collections by Nyangiwe & Horak (2007) were all made during the months January to May (mid-summer to autumn), the period of peak abundance of adult R. appendiculatus in the Eastern Cape Province (Horak 1999).This is also the period of peak adult abundance in the Kruger Na tional Park, which lies immediately to the west of Maputo Province (Horak et al. 1992).In the Mozambican survey 12 of the 21 localities were sampled during June or July, months during which few adults are present, but in which large numbers of larvae and nymphs occur (Horak et al. 1992), as in the present case.
Rhipicephalus appendiculatus is the principal vector of Theileria parva, the causative organism of East Coast fever, one of the most devastating diseases of domestic cattle in East and southern Africa (Lawrence, Perry & Williamson 2004).Theileria parva is not infective to goats (Lawrence et al. 2004), and hence they will not act as reservoirs of the para-site.It might even be so that herding goats with cattle could slightly reduce the risk of the latter animals becoming infected.
Of all tick species that belong to the genus Rhipicephalus in Africa, R. e. evertsi has the most widespread distribution and also has one of the largest host ranges (Walker, Keirans & Horak 2000).The preferred hosts of its adult and immature stages are domestic and wild equids and eland (Norval 1981;Horak et al. 2007), but cattle, goats and sheep are also suitable hosts (Walker et al. 2000).Baker & Ducasse (1968) collected more adult ticks from untreated cattle than from goats at five localities in KwaZulu-Natal Province, whereas Nyangiwe & Horak (2007) collected adult ticks from slightly more goats than from cattle at their 72 sampling localities (Table 2).
Only adult R. simus were collected from both cattle and goats in the present study.This is not surprising as the immature stages infest rodents (Norval & Mason 1981;Rechav 1982).In the study conducted in the Eastern Cape Province by Nyangiwe & Horak (2007), no R. simus were collected from cattle or from goats, even though it was present on dogs sampled at the same localities (Nyangiwe, Horak & Bryson 2006).In the present study the majority of dogs examined concurrently with the cattle and goats were infested (De Matos, Sitoe, Neves, Bryson & Horak 2008).Judging by the number and the variety of hosts infested and the widespread occurrence of R. simus in Maputo Province, the prevailing climate and other environmental conditions are obviously favourable for its survival.

of animals infested with adult ticks Average no. (± SD) of animals infested with adult ticks at each locality No. (proportion) of localities positive for any life stage of each tick species Amblyomma hebraeum
TABLE 1 The relative prevalence of adult ixodid ticks on 105 cattle and 105 goats examined in sets of five at 21 localities in Maputo Province, Mozambique Tick and host species No. (proportion) a 14 (13.3 %) a 2.9 (± 1.82) a 0.62 (± 0.67) a 18 (85.7 %) a 11 (52.4 %) a Pairs of figures in the same column, under the same species name and bearing the same superscript are significantly different (P ≤ 0.05) * = Nymphs and adults and many more adult A. hebraeum were collected from cattle (584) than from goats (71) (Table 2, Fig. 2). A. hebraeum adults and/or nymphs were present on cattle and goats at all 21 sampling localities (Table

TABLE 2
Ticks collected from cattle and goats in the Eastern Cape Province, South Africa and in Maputo Province, Mozambique Nyangiwe & Horak (2007)us (Boophilus) decoloratus and R. (B.) microplus from cattle in Mozambique, but listed only R. (B.) microplus from goats.Baker & Ducasse (1968) recovered a total of 266 R. (B.) microplus in all stages of development in nine consecutive collections from a goat, while the total yield of nine collections each from two calves at the same locality in KwaZulu-Natal Province, South Africa, was 32 692 ticks.Nyangiwe & Horak (2007)recorded 242 collections of R. (B.) microplus from cattle and 113 collections from goats examined at the same localities in the Eastern Cape Province, South Africa (Table De Vos, De Waal & Jackson (2004)the vector both of Babesia bigemina and the more virulent Babesia bovis, the organisms that cause of babesiosis or red water in domestic cattle, whereas the indigenous R. (B.) decoloratus transmits only B. bigemina(Norval & Horak 2004).According toDe Vos, De Waal & Jackson (2004)several factors have led to redwater being recognized as one of the most important diseases of cattle in southern Africa since the latter part of the 20 th century.These authors also state that there is little evidence to suggest that animals other than cattle are important reservoir hosts of these parasites.Hence goats are unlikely to play a role in the epidemiology of redwater should infected ticks feed on them, and their presence on pastures with cattle could perhaps even reduce the chance of the latter animals acquiring infection.