Influence of dipping practices on the seroprevalence of babesiosis and anaplasmosis in the foot-and-mouth disease buffer zone adjoining the Kruger National Park in South Africa.

A serological survey of bovine babesiosis and anaplasmosis was conducted in the foot-and-mouth disease buffer zone surrounding the Kruger National Park in South Africa between 2001 and 2003 to determine whether the withdrawal of government-subsidized dipping in certain regions had affected the seroprevalence of these tick-borne diseases. Seroprevalence of Anaplasma marginale and Babesia bovis increased during the study period. This increase was greater in Limpopo Province where farmers had to supply their own acaricide than in Mpumalanga Province where dipping materials were provided by the local Veterinary Services. The number of animals testing positive for B. bigemina decreased in both provinces during the study period, which was attributed to possible vector displacement rather than more effective tick control measures. Responses to a questionnaire on ticks and tick-borne diseases revealed local knowledge on the subject to be highly variable and sometimes incorrect.

Prevalence and genetic diversity of Anaplasma marginale strains in cattle in South Africa.

Bovine anaplasmosis, caused by the tick-borne rickettsia Anaplasma marginale, is endemic in South Africa and results in considerable economic loss to the cattle industry. This study was designed to characterize strains of A. marginale at the molecular level from cattle raised in communal and commercial farms in the north-eastern and south-western regions of the Free State Province, South Africa, that varied in rainfall and vegetation. Seroprevalence to A. marginale was determined in 755 cattle by an Anaplasma spp. competitive enzyme-linked immunosorbent assay and ranged from 44% to 98% and was similar in both regions. While Anaplasma centrale was not targeted in this study, A. marginale infections were identified by species-specific msp1alpha polymerase chain reaction in 129 of 215 of the samples studied. Similar genetic diversity of A. marginale strains was found in both the north-eastern and south-western regions. The sequences of 29 A. marginalemsp1alpha amplicons from South African strains revealed considerable genetic diversity providing 14 new repeat sequences. However, 42% of MSP1a repeat sequences were not unique to this region. These results indicated the presence of common genotypes between South African, American and European strains of A. marginale. Cattle movement between different parts of South Africa was suggested by the presence of identical A. marginale MSP1a genotypes in north-eastern and south-western regions of the Free State Province. Control strategies for anaplasmosis in South Africa should therefore be designed to be protective against genetically heterogeneous strains of A. marginale.

The effect of orally administered Aloe marlothii leaves on Boophilus decoloratus tick burdens on cattle.

The effect of a decoction of pulverized aloe leaves (Aloe marlothii) mixed with tap water and administered orally through a gastric tube was determined against ticks on cattle. The decoction was administered to six randomly selected calves seven times at 3-day intervals while the remaining calves received an equivalent amount of tap water only. Five hours after first treatment the calves were infested with Boophilus decoloratus larvae hatched from one gram of eggs. Resultant engorged female ticks were collected, counted and weighed daily. Fertility estimates were determined for 30 engorged female ticks collected from each calf in both the treated and control groups of calves. The treatment had no significant effect on total or daily numbers of engorged females collected per group, nor on their biomasses. Fertility estimates showed the treatment group to yield a marginally higher, yet insignificant, egg laying response (ELR) and reproductive estimate (RE).

Effect of burning on the numbers of questing ticks collected by dragging.

Sixteen experimental burn plot replicates, in groups of four, in four landscape zones of the Kruger National Park, South Africa, and from which wildlife are not excluded, have been subjected to fixed, regular burning regimens since 1954. In 1999, a study to determine the effect of burning on ixodid ticks questing for hosts from the vegetation of the plots was initiated, and six sub-plots, with identical histories, within each of two of the burn plot replicates in Combretum collinum/Combretum zeyheyri woodland on granite, were selected. With few exceptions these 12 sub-plots, as well as unburned vegetation adjacent to each of the replicates, were sampled for ticks at monthly intervals for a period of 39 months by dragging with flannel strips. The existing regimen of burning during August or during October on individual sub-plots was continued during this time. A total of 14 tick species was recovered from the plots of which nine could be considered major species. Sufficient numbers for statistical analysis of only eight species were, however, collected. Burning appeared to have little short-term effect on the number of ticks recovered. In the longer term, the response varied from no change, an increase, or a decrease in the numbers of ticks collected each year after burning. Tick species, life cycle, seasonality, questing strategy, host preference and host utilization of the habitat were important determinants of the effect of burning.

Hosts, seasonality and geographic distribution of the South African tortoise tick, Amblyomma marmoreum.

The tortoise tick Amblyomma marmoreum was collected from large numbers of reptiles and other animals during the course of numerous surveys conducted in South Africa. A total of 1229 ticks, of which 550 were adults, were recovered from 309 reptiles belonging to 13 species, with leopard tortoises, Geochelone pardalis being the most heavily infested. The 269 birds sampled harboured 4901 larvae, 217 nymphs and no adult ticks, and the prevalence of infestation was greatest on helmeted guineafowls, Numida meleagris. Only two larvae were recovered from 610 rodents, including 31 spring hares, Pedetes capensis, whereas 1144 other small mammals yielded 1835 immature ticks, of which 1655 were collected from 623 scrub hares, Lepus saxatilis. The 213 carnivores examined harboured 2459 ticks of which none were adult. A single adult tick and 6684 larvae and 62 nymphs were recovered from 656 large herbivores, and a total of 4081 immature ticks and three adults were collected from 1543 domestic animals and 194 humans. Adult male and female A. marmoreum were most numerous on reptiles during January and February, and larvae during March. The largest numbers of larvae were present on domestic cattle and helmeted guineafowls in the Eastern Cape Province during March or April respectively, whereas larvae were most numerous on helmeted guineafowls, scrub hares and the vegetation in north-eastern Mpumalanga Province during May. In both provinces nymphs were most numerous between October and December. Amblyomma marmoreum appears to be most prevalent in the western regions of the Western and Eastern Cape and Free State provinces, and the north-eastern regions of the Northern Cape, KwaZulu-Natal, Mpumulanga and Limpopo provinces.

In vitro cultivation of a south African isolate of an Anaplasma sp. in tick cell cultures.

This paper describes the first successful in vitro cultivation of a South African isolate of an Anaplasma sp., initially thought to be Anaplasma marginale, in the continuous tick cell line IDE8. Blood from a bovine naturally infected with A. marginale kept on the farm Kaalplaas (28 degrees 08' E, 25 degrees 38' S) was collected, frozen, thawed and used as inoculum on confluent IDE8 cell cultures. Twenty days after culture initiation small intracellular colonies were detected in a Cytospin smear prepared from culture supernatant. Cultures were passaged on Day 34. Attempts to infect IRE/CTVM18 cell cultures with the Kaalplaas isolate derived from IDE8 cultures failed, whereas a reference stock of A. marginale from Israel infected IRE/CTVM18 tick cell cultures. Attempts to infect various mammalian cell lines (BA 886, SBE 189, Vero, L 929, MDBK) and bovine erythrocytes, kept under various atmospheric conditions, with tick cell-derived Anaplasma sp. or the Israeli strain of A. marginale failed. Molecular characterization revealed that the blood inoculum used to initiate the culture contained both A. marginale and Anaplasma sp. (Omatienne) whereas the organisms from established cultures were only Anaplasma sp. (Omatjenne).

Comparison of 3 tests to detect acaricide resistance in Boophilus decoloratus on dairy farms in the Eastern Cape Province, South Africa.

The susceptibility of the larval offspring of engorged female Boophilus decoloratus, and of the engorged females, collected from cattle on the dairy farms Brycedale, Sunny Grove and Welgevind in the Eastern Cape Province, South Africa, was tested against the acaricides amitraz, chlorfenvinphos and cypermethrin. Resistance was determined by means of the Shaw Larval Immersion Test (SLIT) for larvae and the Reproductive Estimate Test (RET) and Egg Laying Test (ELT) for adults. At Brycedale the tests all indicated resistance to chlorfenvinphos, and RET and ELT indicated resistance to amitraz and emerging resistance to cypermethrin. At Sunny Grove, B. decoloratus was resistant to cypermethrin using SLIT and exhibited emerging resistance to chlorfenvinphos with SLIT and to cypermethrin with both RET and ELT At Welgevind, resistance was recorded against chlorfenvinphos (SLIT) and against cypermethrin (ELT), and emerging resistance against permethrin (RET). The results obtained with RET and ELT were generally comparable, but often differed from those obtained with SLIT. Resistance could be detected within 7 days with ELT compared to 42 days with RET and 60 days with SLIT.

Acaricide resistance profiles of single- and multi-host ticks from communal and commercial farming areas in the Eastern Cape and North-West Provinces of South Africa.

A field study (February 2000 to August 2001) was conducted on communal and commercial farms in the Eastern Cape and North-West Provinces of South Africa to detect the levels of tick resistance to commonly used acaricides. The larvae obtained from engorged females of the one-host tick Boophilus decoloratus, the two-host tick Rhipicepalus evertsi evertsi and the three-host ticks Amblyomma hebraeum and Rhipicephalus appendiculatus were tested against various concentrations of amitraz, chlorfenvinphos and cypermethrin using the Shaw Larval Immersion Test method. Ticks from the communal farms showed higher levels of resistance to cypermethrin and some resistance to chlorfenvinphos whilst no resistance was detected against amitraz. However, ticks from commercial farms were equally resistant to amitraz, chlorfenvinphos and cypermethrin. The B. decoloratus populations tested were considerably more resistant to all the acaricides tested than the R. evertsi evertsi, A. hebraeum and R. appendiculatus populations. This supports the hypothesis that single-host ticks develop resistance faster than multi-host ticks. This trend was recorded on most of the farms where single- and multi-host ticks co-existed. It was concluded that the use of acaricides at high frequencies and high concentrations was one of the main causes of tick resistance in the study areas. Possible factors which caused the resistance problems are discussed and acaricide management strategies recommended.

Parasites of domestic and wild animals in South Africa. XL. Ticks on dogs belonging to people in rural communities and carnivore ticks on the vegetation.

Ixodid ticks were collected at weekly intervals from February 1999 to April 2000 from domestic dogs belonging to people in rural communities in north-eastern KwaZulu-Natal. Seven ticks were identified to species level and adult Haemaphysalis leachi followed by immature Amblyomma hebraeum and adult Rhipicephalus simus were the most prevalent. Infestation with adult H. leachi was most intense during February and March 1999 and from January to April 2000, and least intense during October 1999. Infestation with adult R. simus was most intense during February and March 1999 and least during July and September of the same year. For 12 consecutive years, from August 1988 to July 2000, free-living ticks were collected at monthly intervals from the vegetation of two landscape zones in the Kruger National Park. Most adult H. leachi were collected in the one zone from March to June, and no ticks were collected in October, whereas, with the exception of March, most were collected in the other zone during the period January to June, and only one tick was collected in October. Most adult R. simus were collected during February and March at both localities and only a single tick was collected in September. Adult Rhipicephalus turanicus was present only in the one zone and was collected only from January to June.

Parasites of domestic and wild animals in South Africa. XXXIII. Ixodid ticks on scrub hares in the north-eastern regions of northern and eastern Transvaal and of KwaZulu-Natal.

Ixodid ticks were collected from scrub hares (Lepus saxatilis) at three localities. Nine tick species were recovered from 24 hares examined at Pafuri, Kruger National Park, Northern Transvaal. The most abundant and prevalent species were Hyalomma truncatum, Rhipicephalus kochi and a Rhipicephalus species (near R. pravus). Twelve tick species were collected from 120 scrub hares examined around Skukuza, Kruger National Park, Eastern Transvaal. The immature stages of Hyalomma truncatum were most abundant and those of Amblyomma hebraeum most prevalent on the hares. No haematozoa were found on blood smears made from these hares. Thirty-four scrub hares on mixed cattle and game farms near Hluhluwe, north-eastern KwaZulu-Natal harboured 12 tick species. The most abundant and prevalent of these were the immature stages of Rhipicephalus muehlensi. Piroplasms, tentatively identified as Babesia leporis, were present on blood smears of eight of these hares. The host status of scrub hares for 18 ixodid tick species or subspecies found in South Africa is tabulated.

Isolation and characterization of an anticoagulant present in the salivary glands of the bont-legged tick, Hyalomma truncatum.

A low molecular mass anticoagulant (17 kDa) was isolated from the salivary glands of prefed female Hyalomma truncatum ticks by means of reverse phase and anion-exchange HPLC. Trypsin digestion and amino acid analysis confirmed the protein nature of the anticoagulant. The inhibitor appears to be uncompetitive with a Ki of 6.9 x 10(-10)M. The target of the anticoagulant is factor Xa at the junction of the extrinsic and intrinsic pathways. This may be crucial for the survival of the tick, making it feasible to investigate the possibility of vaccination with this antihaemostatic against tick feeding. In addition, tick anticoagulants may possibly have therapeutic application in controlling thrombosis.

Tick ecology.

The availability and expediency of acaricides for the control of ticks, together with the development of vaccination procedures against tick-borne diseases as a matter of priority, initially preceded information gained from research on tick ecology. The establishment of acaricide resistance, the increasing cost of chemical control and the data on production loss as an integral part of tick infestation are factors which led to the incorporation of ecological principles into tick control. Continuing research on the life processes of ticks as well as on their interaction with hosts and the environment, initiated producer manipulation of acaricide application frequencies, habitat manipulation techniques and the use of host immunity which are important for the establishment of economically suitable strategies of tick control. The role of tick ecology in establishing these concepts and its influence on current tick research is examined.

Parasites of domestic and wild animals in South Africa. XXXII. Ixodid ticks on scrub hares in the Transvaal.

A total of 264 scrub hares (Lepus saxatilis) were examined for ixodid ticks at various localities in the Kruger National Park, eastern Transvaal Lowveld. Thirteen tick species were recovered from these hares. The seasonal abundances of the immature stages of Amblyomma hebraeum, Amblyomma marmoreum, Hyalomma truncatum, Rhipicephalus appendiculatus, Rhipicephalus evertsi evertsi, Rhipicephalus simus and Rhipicephalus zambeziensis and all stages of a Rhipicephalus sp. (near R. pravus) were determined. Three scrub hares, examined in the north-western Transvaal Bushveld, were infested with five ixodid tick species. Ten hares examined in the eastern Transvaal Highveld harboured three species. A total of 15 ixodid tick species were recovered from the scrub hares examined in the three regions of the Transvaal. No haematozoa were found in blood smears made from the hares examined in the southern region of the Kruger National Park.

Parasites of domestic and wild animals in South Africa. XXX. Ectoparasites of kudus in the eastern Transvaal Lowveld and the eastern Cape Province.

Sets of four kudus were shot and examined for arthropod parasites at approximately monthly intervals from April 1981 to March 1983 in the southern part of the Kruger National Park, eastern Transvaal Lowveld. These animals harboured 10 ixodid tick species of which Boophilus decoloratus followed by Amblyomma hebraeum were the most abundant. The seasonal abundances of these ticks and of Amblyomma marmoreum, Rhipicephalus appendiculatus, Rhipicephalus evertsi evertsi and Rhipicephalus zambeziensis were determined. The kudus were also infested with 3 lice and 1 louse fly species, as well as the nymphs of a pentastomid. Sixteen kudus were shot in the Andries Vosloo Kudu Reserve, eastern Cape Province and 9 on an adjacent farm. These animals were infested with 12 tick species. A. hebraeum followed by Rhipicephalus glabroscutatum were the most abundant on kudus in the reserve and R. glabroscutatum followed by Haemaphysalis silacea on the animals on the farm. The seasonal abundances of A. hebraeum, A. marmoreum, H. silacea, R. appendiculatus, R. glabroscutatum and a Rhipicephalus sp. (near R. oculatus) were determined on the kudus in the reserve. The kudus were also infested with 3 lice and 1 louse fly species. Two kudus examined in the Addo Elephant National Park were infested with 6 tick, 1 louse and 1 louse fly species.

The effect of veld-burning on the seasonal abundance of free-living ixodid ticks as determined by drag-sampling.

A supervised veld-burn in the Sclerocarya caffra/Acacia nigrescens Savanna landscape zone in the south-eastern region of the Kruger National Park was carried out during September 1988. The effect of the fire on the free-living tick population was determined by comparing the numbers of ticks collected by monthly drag-sampling in the burnt zone with those collected in an adjacent unburnt zone over a 2-year period. A total of 13 ixodid tick species were involved. Tick numbers were reduced after the burn but rose again after varying periods of time. The length of these periods depended upon a number of variables. These included tick species, patterns of seasonal abundance, and host preferences. The original reduction in numbers seemed to result in subsequent cyclical population fluctuations and in some instances overcompensation was noted. Veld-burning as a control technique may be effective with tenuously adapted tick species or reduced populations and may be enhanced by the exclusion of major hosts for a critical period after the fire.

A survey of small stock tick control practices in the eastern Cape Province of South Africa.

Current small stock tick control practices and producer attitudes towards tick control in the eastern Cape Province of South Africa are discussed. These were ascertained from returns to a questionnaire survey to which 31.2% of farmers polled, responded. In general, producers did not favour an intensive tick control policy for small stock. Angora, mutton and wool farmers had a definite preference for synthetic pyrethroid acaricides, the majority treating either less than 6 times p.a. or between 11-15 times p.a. Most producers changed acaricides because of price. All small stock producers favoured plunge dip application of acaricides while the majority of wool sheep and Angora producers utilized footbath application as a second preference. Mutton producers favoured pour-on and hand spray application as a second choice. Producers who used plunge dip application techniques experienced the highest percentage of confirmed acaricide resistance which is in accordance with application preference. The general incidence of confirmed acaricide resistance, however, was of a low order but highest amongst mutton farmers. An average cost for acaricide treatment of R1.65 per small stock unit p.a. was calculated from data gained in this survey. Only a small number of producers used the available heartwater vaccine. Small stock mortalities experienced by producers per production unit indicated higher mortalities at high acaricidal treatment frequencies. Farmers allowing a small number of ticks to infest their sheep experienced fewer mortalities due to heartwater than those than kept their sheep free of ticks. Angora goat farmers experienced the same, but with higher mortalities, probably due to the apparently high susceptibility of Angora goats to heartwater.

A survey of cattle tick control practices in the eastern Cape Province of South Africa.

Current cattle tick control practices and producer attitudes towards tick control in the eastern Cape Province of South Africa are discussed. These were ascertained from answers to a questionnaire survey to which 31.2% of farmers responded. In general, producers favoured intensive tick control. Beef and dairy farmers had a definite preference for synthetic pyrethroid acaricides, the majority followed a 25 times p.a. treatment frequency and most changed acaricides because of price. Beef producers favoured pour-on application of acaricides while the majority of dairy producers utilized plunge dipping. Producers who used hand spray techniques experienced the highest percentage of confirmed acaricide resistance. A costs of R11.27 for acaricide treatment per bovine per annum was calculated from data gained in this survey. A cost index of 2,496 was calculated by relating acaricide cost to the prevailing price of beef in the region. Only a small number of producers used heartwater, babesiosis and anaplasmosis vaccines. Relative tick borne disease mortality ratios indicated higher heartwater mortalities at high acaricide treatment frequencies. These results are discussed in relation to the tick control regimes practised.

The identification of a shared immunogen present in the salivary glands and gut of ixodid and argasid ticks.

The identification of a 70-kDa immunogen present in salivary gland extracts of several ixodid species, namely Hyalomma truncatum (sweating-sickness-inducing (SS+) and non-inducing (SS-) strains), Hyalomma marginatum rufipes and Rhipicephalus evertsi evertsi, is reported. The immunogen was identified by Western blots using a monoclonal antibody of the IgM isotype directed against a 70-kDa immunogen present in the salivary glands of (SS-) female H. truncatum ticks. Cross-reactivity with the gut of unfed adult ixodid ticks, Amblyomma hebraeum, Rhipicephalus simus simus, R. evertsi evertsi, Rhipicentor nuttali, H.m. rufipes, and salivary glands of adult argasid species, Ornithodoros savignyi and Ornithodoros moubata, was demonstrated using ELISA.

Immunization of guinea-pigs and cattle against adult Rhipicephalus appendiculatus ticks using semipurified nymphal homogenates and adult gut homogenate.

Guinea-pigs inoculated with crude homogenate of unfed nymphs of the tick Rhipicephalus appendiculatus and with three semipurified fractions of the homogenate obtained by gel permeation chromatography, acquired a significant degree of immunity to infestation with adults of this tick. Fraction 2 induced the highest reduction (66%) in mean weight of engorged females followed by crude homogenate and fractions 1 and 3. Calves immunized with crude homogenates of unfed nymphs, fraction 2 of nymphal homogenate, and gut homogenate of unfed females also acquired immunity against adults of R. appendiculatus. The mean weight of engorged females fed on calves inoculated with nymphal fraction 2 was the lowest of all five groups of calves on which females fed. The reduction in weight (38%) was not significantly different from that observed for females fed on calves inoculated with crude nymphal homogenate (31%) or females from third infestation of adult ticks. No differences in the weight and hatchability of egg batches produced by engorged females collected from the five groups of calves were observed. Analysis of sera collected from the five groups of calves showed that the concentration of albumin, alpha-1, alpha-2 and beta-globulins fluctuated and no significant differences between the treated groups were observed. The levels of gamma-globulin increased in treated groups including the group inoculated with adjuvant only, but unlike previous reports no increase in gamma-globulin or a correlation between the level of gamma-globulin and the degree of resistance acquired were observed in calves exposed to repeated tick infestations. However, the increase in the concentration of gamma-globulin in calves inoculated with fraction 2 or crude nymphal homogenate was higher than that observed in the other groups.

Parasites of domestic and wild animals in South Africa. XXVII. Ticks on helmeted guineafowls in the eastern Cape Province and eastern Transvaal Lowveld.

Seventy-six helmeted guineafowls (Numida meleagris) were shot in the Andries Vosloo Kudu Reserve and on an adjacent farm in the eastern Cape Province during the period May 1985 to January 1987 and their tick burdens determined. A total of 10 ixodid tick species were recovered, of which Amblyomma hebraeum, Amblyomma marmoreum and Haemaphysalis silacea were the most abundant. The seasonal abundances of these 3 species and of Hyalomma marginatum rufipes were ascertained. A marked difference between the total number of A. hebraeum recovered from the birds in the reserve and those on the farm is ascribed to the treatment of domestic stock on the farm with an acaricide. The tick burdens of 118 helmeted guineafowls, shot in the southern part of the Kruger National Park, eastern Transvaal Lowveld, from August 1988 to August 1990, were also determined. Ten ixodid tick species and the larvae of an argasid species were recovered. A. hebraeum, A. marmoreum and the Argas sp. were the most abundant and their seasonal abundances and that of Rhipicephalus zambeziensis were determined. Only 2 of the 54,659 ixodid ticks recovered from the birds at the 3 localities were adults and the presence of these is ascribed to accidental infestations.