The productivity effects of cattle tick (Boophilus microplus) infestation on cattle, with particular reference to Bos indicus cattle and their crosses

In response to uncertainty among cattle producers in Australia regarding the need to treat Bos indicus and B. indicus crossbreeds, the scientific literature relating to the productivity effects of Boophilus microplus on cattle of all breeds was reviewed. Estimates of the mean effect of each engorging tick (damage coefficient, d) were made from a simple analysis of the reported data. On average, each engorging female tick is responsible for the loss of 1.37 +/- 0.25 g bodyweight in B. taurus cattle. The comparable value for B. taurusxB. indicus cattle is 1.18 +/- 0.21 g/engorging tick. These values were not statistically significantly different, indicating that if a threshold approach to tick control were taken, then the threshold number of standard ticks would be the same regardless of cattle genotype. No studies provided useable estimates of the effect of tick infestation on pure B. indicus cattle. An economic threshold for treatment, below which acaricide application is not beneficial, can be predicted, using known values for the cost of acaricide application and the price of beef. However, the application of a threshold approach to control has not been embraced by government advisers and runs contrary to the accepted principals of strategic control programs.     

Class I antigens of the bovine major histocompatibility system and resistance to the cattle tick (Boophilus microplus) assessed in three different seasons

Two consecutive calf crops consisting of 141 three-quarters Brahman/one-quarter Shorthorn cattle were assessed for resistance to the Australian cattle tick Boophilus microplus in May, July and October 1983. Although the level of expressed resistance to artificial infestation varied considerably between seasons, the animals maintained very similar rankings for resistance in all three seasons, and the repeatability of tick resistance ranged from 0.59 to 0.82. The cattle were typed for 30 bovine class I lymphocyte antigens. Antigens W6 and CA31 were associated with susceptibility to artificial tick infestation but none of the other lymphocyte antigens showed strong associations with resistance or susceptibility.     

Histopathology of attachment sites of Amblyomma variegatum and Rhipicephalus appendiculatus on zebu cattle of varying resistance to ticks.

Mature, unimproved East African Zebu cattle (Bos indicus) naturally exposed to ticks from birth were ranked for resistance to ticks by repeated whole-body counts of infesting ticks. Four cattle of high resistance, four of low resistance and two of intermediate resistance were artificially infested with nymphs of Amblyomma variegatum and Rhipicephalus appendiculatus. Two Friesian cattle (Bos taurus) with less exposure to ticks were similarly infested. Biopsies of tick attachment sites were examined histologically. All attachment sites showed acute inflammatory lesions, and sites of both tick species on high resistance cattle showed delayed hypersensitive reactions with intra-epidermal pustulation and significant increases in the numbers of granulocytes. The predominant cells infiltrating attachment sites on high resistance cattle were eosinophils with A. variegatum and neutrophils with R. appendiculatus. Such differences need to be taken into account in developing immunological tests for selecting cattle for resistance but there are sufficient common features of reactions to the two infesting tick species to justify dermal hypersensitivity tests.     

Relative resistance of six cattle breeds to the tick Boophilus decoloratus in South Africa

Adult females of the tick Boophilus decoloratus were removed from 6 breeds of cattle on 2 farms in the Northern Transvaal. Highest numbers of female ticks were collected from Simmentaler, followed by Santa Gertrudis, Bonsmara, Afrikaner, Brahman and Nguni. Resistance levels of each breed to B. decoloratus was positively correlated with the amount of Bos indicus genes in the breed, with the exception of Nguni, which is a sanga type but not pure B. indicus.     

Resistance of Holstein-Friesian cows to infestation by the cattle tick (Boophilus microplus)

In two experiments, the milk production of 59 Holstein-Friesian cows in mid lactation was measured over 1 week before artificial infestation with 2,500 or 5,000 Boophilus microplus larvae. Host resistance, the proportion of female ticks applied but not engorging was estimated from weekly counts of engorging female ticks of 4.5-8. 0mm long. Mean host resistance was 79 and 67% in two experiments. Host resistance was not significantly related to milk yield before infestation, to early pregnancy, or to parity. Culling the 10% of cattle with the least resistance to ticks would result in removal of 19-21% of ticks in a herd. The results suggest that selection to improve the existing low levels of resistance to B. microplus might be undertaken without compromising milk production. However, low levels of resistance among the cattle studied and difficulties in assessment of resistance are likely to limit the usefulness of selection within the Holstein-Friesian breed.     

Decreased resistance of Bos taurus cattle on a diet supplemented with whole cotton seed to the tick Boophilus microplus (Canestrini)

Resistance to the tick B. microplus was compared in Bos taurus steers fed hay (low fat (LF) diet) with those fed hay supplemented with whole cotton seeds (high fat (CS) diet) which made them hyperlipidaemic. The mean number of adult female ticks maturing from the same artificial doses of larvae was about 2.7 times higher on animals fed the CS diet than on animals fed the LF diet. In both dietary groups the effect of ticks: depressed packed-cell volume, plasma cholesterol and phospholipid levels, serum albumin levels, serum alkaline phosphatase (EC 3.1.3.1) and amylase (EC 3.2.1.1) activities, and monocyte count; increased the serum level of gamma-globulin and eosinophil count. Animals on the LF diet responded to tick infestation with an increase in the number of circulating lymphocytes and a decrease in the neutrophil count. In contrast, the lower tick resistance in hyperlipidaemic animals on the CS diet was associated with a decrease in the number of lymphocytes.     

A new single nucleotide polymorphism in CAPN1 extends the current tenderness marker test to include cattle of Bos indicus, Bos taurus, and crossbred descent

The three objectives of this study were to 1) test for the existence of beef tenderness markers in the CAPN1 gene segregating in Brahman cattle; 2) test existing CAPN1 tenderness markers in indicus-influenced crossbred cattle; and 3) produce a revised marker system for use in cattle of all subspecies backgrounds. Previously, two SNP in the CAPN1 gene have been described that could be used to guide selection in Bos taurus cattle (designated Markers 316 and 530), but neither marker segregates at high frequency in Brahman cattle. In this study, we examined three additional SNP in CAPN1 to determine whether variation in this gene could be associated with tenderness in a large, multisire American Brahman population. One marker (termed 4751) was associated with shear force on postmortem d 7 (P < 0.01), 14 (P = 0.015), and 21 (P < 0.001) in this population, demonstrating that genetic variation important for tenderness segregates in Bos indicus cattle at or near CAPN1. Marker 4751 also was associated with shear force (P < 0.01) in the same large, multisire population of cattle of strictly Bos taurus descent that was used to develop the previously reported SNP (referred to as the Germplasm Evaluation [GPE] Cycle 7 population), indicating the possibility that one marker could have wide applicability in cattle of all subspecies backgrounds. To test this hypothesis, Marker 4751 was tested in a third large, multisire cattle population of crossbred subspecies descent (including sire breeds of Brangus, Beefmaster, Bonsmara, Romosinuano, Hereford, and Angus referred to as the GPE Cycle 8 population). The highly significant association of Marker 4751 with shear force in this population (P < 0.001) confirms the usefulness of Marker 4751 in cattle of all subspecies backgrounds, including Bos taurus, Bos indicus, and crossbred descent. This wide applicability adds substantial value over previously released Markers 316 and 530. However, Marker 316, which had previously been shown to be associated with tenderness in the GPE Cycle 7 population, also was highly associated with shear force in the GPE Cycle 8 animals (P < 0.001). Thus, Marker 316 may continue to be useful in a variety of populations with a high percentage of Bos taurus backgrounds. An optimal marker strategy for CAPN1 in many cases will be to use both Markers 316 and 4751.     

Relationship between the resistance of cattle to Haemaphysalis longicornis and to Boophilus microplus

Cattle that had been exposed to Haemaphysalis longicornis were as susceptible to Boophilus microplus as cattle that had never been exposed to either species of tick. Cattle with acquired resistance to both species ranked consistently for levels of resistance to each when infested separately. Concurrent infestation with H. longicornis had no effect on ranking for resistance to B. microplus. The coefficient of concordance between the rankings of individuals on their levels of resistance to both species of tick was positive, but was not statistically significant. We conclude that the tick antigens that stimulate host resistance are species-specific and do not cross protect. The apparent correlation in rankings for resistance to the 2 species may be a consequence of either an individual's immunological responsiveness to tick antigens or to non-specific host factors which determine levels of resistance. The apparent correlation suggests that co-selection for resistance to different tick species is practicable.     

Allele frequencies of gene polymorphisms related to economic traits in Bos taurus and Bos indicus cattle breeds

Allele frequencies of 10 representative polymorphisms for beef and milk traits were investigated for a total of 240 animals from Bos taurus and Bos indicus breeds, including two Japanese groups (Japanese Black and Japanese Brown), two East Asian groups (Korean and Mongolian), three European groups (Holstein, Angus and Hereford) and a Bos indicus group in South Asia (Myanmar, Laos and Cambodia). The Japanese Black revealed unique genetic construction in GH, FASN and SREBP‐1 and the other Asian populations show intermediate frequencies between European and Japanese populations. The Bos indicus group showed low favorable allele frequencies in most of the genes. The study showed the variability and distribution of 10 genes affecting economic traits among world representative cattle breeds. The genetic information would contribute to elucidating the genetic background for worldwide cattle breeds and the possibility of improvement using the markers.     

Bos taurus Y chromosome of Africander cattle and the development of improved breeds for the tropics.

The Africander has anatomical and other characteristics of an animal of approximately 3/4 Bos indicus heredity. The fact that these cattle carry the Bos taurus Y chromosome supports this view and indicates that the local cattle in South Africa would have been crossed with one or more Bos taurus bulls. Droughtmaster and Braford cattle retain the Bos indicus Y chromosome because Bos indicus instead of Bos taurus bulls were used to establish these taurindicus breeds. Contrary to some assumptions, an approximate tenfold increase in productivity of cattle was made during the 18th and 19th centuries due to improvements in disease control, nutrition and genetic improvement. What is now needed is the development of taurindicus breeds combining to the maximum possible extent the disease resistance and hardiness of Bos indicus with the early maturity and productivity of Bos taurus cattle. In addition, the ravages of disease and the seasonal variations of food supply need to be overcome in tropical areas.     

Ticks and tick-borne disease in Guatemalan cattle and horses

Blood samples and ticks were collected from 48 cattle and 74 horses from seven sites in the Peten region of Guatemala. Data on body condition, mucous membrane capillary refill time and tick infestation levels were recorded for each animal in the study. Horses had significantly higher levels of tick infestation than cattle, as well as poorer body condition scores. Seroprevalence of Babesia spp. was 95.8% for B. bovis in cattle, 89.6% for B. bigemina in cattle, and 92.7% for B. equi in horses. Seroprevalence of Anaplasma marginale in cattle was 87.5%, similar to reports in animals from other regions of Central America. This is the first time that A. phagocytophilum has been reported in animals from this region, with overall PCR-prevalence of 27.6% in cattle and horses, and seroprevalence of 28.4% (52% in cattle and 13% in horses). An agent was identified with serological cross-reactivity and close genetic relatedness to Ehrlichia ruminantium, but further testing confirmed that the agent in Guatemalan cows was not the agent of heartwater. Ticks were identified to species with the predominant species identified on cattle as Boophilus microplus and Amblyomma cajennense, while Anocentor nitens and A. cajennense were most commonly found on horses. Prevalence of infection, tick infestation levels, host factors and environmental data were analyzed for association; A. nitens was significantly associated with A. phagocytophilum prevalence by village.     

A survey of cattle producers in the Boophilus microplus endemic area of Queensland to determine attitudes to the control of and vaccination against tick fever

SUMMARY: A survey by mail was used to determine the views of beef producers in the Boophilus microplus endemic area of Queensland on the control of and vaccination against tick fever. Data from 448 questionnaires were analysed, representing 2.7% of beef producers in the survey area. Producers considered buffalo fly ( Haematobia irritans exigua ) infestation as the most important problem whereas tick fever ranked sixth overall. Private veterinarians were regarded as the most important source of information on vaccines for cattle followed by a weekly rural newspaper. From the survey we estimate that about 33% of producers used the tick fever vaccine produced by the Tick Fever Research Centre of Queensland Department of Primary Industries but there were significant (P < 0.05) variations between regions and herds. Large herds (≥ 400 head) in south-east Queensland were the most likely to be vaccinated against tick fever. Of the producers who did not use the vaccine, over 70% replied that there was no need to vaccinate because of the low risk of the disease in their herds. In 52% of unvaccinated herds the treatment of animals with acaricide was considered the most important means of tick fever control and 61% of these herds comprised Bos indicus x Bos taurus or Bos indicus cattle.     

Factors related to cattle infestation level and resistance to acaricides in Boophilus microplus tick populations in New Caledonia

Boophilus microplus, even in the absence of babesiosis, is a major disease of the cattle in New Caledonia where the particular farming system associates continental European breeds and a tropical climate tempered by the Pacific Ocean. In order to have a better understanding of the factors involved in cattle tick infestation, to decrease the possible wastage and use of chemicals and to increase the lifetime of the acaricides, the veterinary authorities investigated the conditions of the chemical treatments. A survey among 148 cattle farms of the whole of New Caledonia was carried out and factors that explain the development of tick resistance and cattle infestation have been determined. From this survey, three typologies for the main characteristics of the farms have been set up, the technical practices of the farmers and the tick control measures applied by the farmers, respectively. Some variables are significantly associated with the tick resistance to deltamethrin but their contribution to the explanation model is always moderate: farms in the south, with a positive resistance gradient from east to west, absence of bush fire and membership to a cattle farmers organization. The more the farmers have intensified their breeding-male castration, weaning, heifer separation, drenching, etc.-and pasture-high stock rate, mowing, extra feeding of the cows, many paddocks, etc.-techniques, the higher was the probability for the ticks in their farm to be resistant to deltamethrin. The technical details of the acaricide treatment had a low contribution to the explanation model. However, the use of a spray generated more resistance than a dip. Furthermore, there is a negative resistance gradient when the farmers increased the treatment interval average. Considering infestation, none of the variables from the three typologies were associated with the two infestation variables (1: semi-engorged tick females and 2: other ticks) at the herd level. However, the seven studied variables-the three typologies, breed, age, body condition score and breeding status-affected significantly the two infestation variables at the cow level, but their predictive ability remained very low (R(2)<3.5%). This result-individual effect more important than herd effect on the infestation-is confirmed by the importance of the variance of the intra-farm factors (99%) when compared with inter-farm factors (1%). Cows of Charolais breed, in poor body condition, old, pregnant or lactating, and those of the farms with irrational and high pressure control of ticks are the most infested.     

Relationship between the resistance of crossbred cattle to ticks, Boophilus microplus (Canestrini, 1887) and Hyalomma anatolicum anatolicum (Koch, 1844)

Studies were undertaken to determine the effect of repeated pure infestations with Boophilus microplus on susceptibility to subsequent pure infestations with Hyalomma anatolicum anatolicum, and the effects of pure infestations with both species of tick on susceptibility to a series of mixed infestations. Crossbred (Bos indicus X Bos taurus) calves were infested with Boophilus microplus (17 times), H. a. anatolicum (four times), followed by five mixed infestations of B. microplus and H. a. anatolicum. The decline in B. microplus engorgement from a mean yield of 274.4 +/- 60.3 ticks per host after the first exposure, to a mean yield of 9 +/- 4.6 per animal after the seventeenth exposure, was observed in animals exposed to only B. microplus. This might be due to acquired resistance. However, these animals were found to be as susceptible to H. a. anatolicum as animals which had never been exposed to ticks of either species. A decline in the yield of H. a. anatolicum from a mean yield of 92.1 +/- 10.7 after the first exposure to 54.7 +/- 11.3 after the fourth exposure, indicated that the cattle could also acquire resistance to repeated pure infestations with this species. After repeated pure infestations with both tick species, cattle reacted to five mixed infestations showing a high degree of resistance to B. microplus and low resistance to H. a. anatolicum (mean yield for B. microplus was only 10 +/- 8.1 ticks per host after the first mixed exposure and declined to 1.3 +/- 1.7 after the fifth, whereas the mean yield for H. a. anatolicum was 71.4 +/- 11.3 ticks per host following the first exposure and declined to 37.3 +/- 7.8 after the fifth). Host responses elicited to one species do not provide cross-resistance to the second species used in this study.     

Effects of tick infestation on Boran (Bos indicus) cattle immunised against theileriosis in an endemic area of Kenya

Boran (Bos indicus) heifers were immunised by infection with local Theileria parva parva, T p lawrencei and T mutans stocks and treated with parvaquone and later exposed to natural tick and tick-borne disease challenge in the Trans-Mara Division of Kenya. The Theileria species parasites in the challenge were maintained in African buffalo and cattle and the tick vectors were supported by several species of wild Bovidae and domestic livestock present in the area. Thirty immune cattle were observed for 30 weeks while grazing on a ranch in the Trans-Mara Division. Of these, 15 were immersed in toxaphene at weekly or twice-weekly intervals while 15 cattle remained without acaricide application. Cattle which became pregnant were withdrawn from the experiment. There was no evidence of any clinical tick-borne disease in either group of cattle during the experiment. Five species of ixodid ticks infested the cattle during the experiment and cattle which were not treated with acaricide had far more ticks. Rhipicephalus appendiculatus was the most abundant tick species, with a mean infestation of 46 adults per animal in the undipped cattle. This tick also appeared to be the cause of the observed reduction in weight gains. Major haematological parameters did not differ significantly between the groups. Behavioural studies showed that the undipped cattle spent less time grazing and ruminating. This study has shown that, at the expense of some loss in productivity, zebu cattle, immunised against ticks and theileriosis, can be kept despite tick infestation.     

Genetic resistance of hosts and its influence on epidemiology

Evidence for the genetic control of resistance of sheep to gastrointestinal nematode infections was reviewed and compared with that of cattle to infestation with the cattle tick. Variation within sheep breeds in resistance to nematode infection is as great as that between breeds, is moderately heritable, and selection of lines of resistant sheep should result in animals carrying worm burdens around 10%-20% of those of unselected animals. The consequences of genetically resistant sheep for the epidemiology of Trichostrongylus colubriformis infection were examined with the aid of a simulation model. Predicted results were similar to those observed in cattle herds resistant to Boophilus microplus; seasonal peaks in parasite burdens were greatly reduced, and larval numbers on pasture were reduced even further. The use of genetically resistant hosts should permit a reduced frequency of anthelmintic treatment, and hence reduce the rate of development of anthelmintic resistance in the parasite.     

Immune responses of infected and vaccinated Hereford cattle to antigens of the cattle tick, Boophilus microplus

Responses of infested and vaccinated Hereford cattle to Boophilus microplus antigens were measured by enzyme-linked immunosorbent assay (ELISA), lymphocyte blastogenesis assay (LBA) and intradermal skin tests. Responses against soluble salivary gland extracts (SGS), salivary gland membrane (SGM), soluble gut extracts (GS), gut membrane (GM), soluble larval extracts (LS) and larval membrane (LM) antigens were tested. In one experiment, cattle infested with up to 160,000 ticks had positive cellular responses to SGS and significant antibodies against LM, GM, SGM, and SGS. Cellular responses to Concanavalin A were not depressed following infestation. Cattle vaccinated with GM, using Quil A as adjuvant, had positive cellular responses to gut and salivary gland antigens and significant antibody responses to all antigens tested. The antibody levels of vaccinated cattle were significantly higher than the antibody levels of infested cattle (P less than 0.05). In a second experiment, immune responses of cattle infested with 40,000 ticks were studied during 38 days. Cellular responses in LBA to several tick antigens were transiently elevated and significant levels of antibody were measured against LM, GM, SGM and SGS, from day 25 (P less than 0.05). Infested cattle had positive skin reactions following intradermal injection of larval and adult tick antigens (P less than 0.05).     

Productivity and health effects of anaplasmosis and babesiosis on Bos indicus cattle and their crosses, and the effects of differing intensity of tick control in Australia

Tick fever is an important disease of cattle where Rhipicephalus (Boophilus) microplus acts as a vector for the three causal organisms Babesia bovis, Babesia bigemina and Anaplasma marginale. Bos indicus cattle and their crosses are more resistant to the clinical effects of infection with B. bovis and B. bigemina than are Bos taurus cattle. Resistance is not complete, however, and herds of B. indicus-cross cattle are still at risk of babesiosis in environments where exposure to B. bovis is light in most years but occasionally high. The susceptibility of B. indicus cattle and their crosses to infection with A. marginale is similar to that of B. taurus cattle. In herds of B. indicus cattle and their crosses the infection rate of Babesia spp. and A. marginale is lowered because fewer ticks are likely to attach per day due to reduced numbers of ticks in the field (long-term effect on population, arising from high host resistance) and because a smaller proportion of ticks that do develop to feed on infected cattle will in turn be infected (due to lower parasitaemia). As a consequence, herds of B. indicus cattle are less likely than herds of B. taurus cattle to have high levels of population immunity to babesiosis or anaplasmosis. The effects of acaricide application on the probability of clinical disease due to anaplasmosis and babesiosis are unpredictable and dependent on the prevalence of infection in ticks and in cattle at the time of application. Attempting to manipulate population immunity through the toleration of specific threshold numbers of ticks with the aim of controlling tick fever is not reliable and the justification for acaricide application should be for the control of ticks rather than for tick fever. Vaccination of B. indicus cattle and their crosses is advisable in all areas where ticks exist, although vaccination against B. bigemina is probably not essential in pure B. indicus animals.     

Whole-genome resequencing reveals diversity,global and local ancestry proportions in Yunling cattle

Yunling cattle, a three-breed cross consisting of 1/2 Brahman cattle, 1/4 Murray Grey cattle and 1/4 Yunnan Yellow cattle, has advantage of rapid growth, good meat quality, enhanced tolerance towards a hot and humid climate, tick resistance and crude feed forbearance. Here, we investigated the genetic diversity, global and local ancestry proportions by sequencing the genomes of 131 Yungling cattle and 31 Brahman cattle (for control). Furthermore, we used 35 published genomes of ancestry breeds (including Angus cattle [ancestry of Murray Grey], Wannan cattle [ancestry of Yunnan Yellow cattle: Wenshan and Dianzhong], Wenshan and Dianzhong cattle) to characterize the formation process of Yunling cattle. The highest nucleotide diversity was found in the Wannan cattle, followed by Wenshan, Dianzhong, Brahman, Yunling and Angus cattle. The results of LD decay in each breed was largely consistent with the results of nucleotide diversity, except for the faster decay in Angus cattle out of a smaller effective population size and a strong bottleneck during the breed formation. The population-structure analysis revealed that the cross-breed Yunling cattle harboured the ancestry with Angus (0.44), Brahman (0.48) and Wannan cattle (0.08). Subsequently, we used RFmix to infer local ancestry in Yunling cattle and then performed chi-squared test to obtain the segments whose proportions of a certain ancestry were excessive compared with the whole-genome level, leading to 391 Angus, 49 Brahman and 2,312 Wannan segments. Gene annotation and KEGG enrichment analysis revealed that the excessive Angus, Brahman and Wannan segments might contribute to the rapid growth, immune resistance and indigenous adaptation, respectively, in Yunling cattle. Our results help understand ancestry components and formation process in Yunling cattle and will provide an opportunity for selective breeding by molecular approaches in future.     

Parasite burdens and host susceptibility of Zebu and N'Dama cattle in village herds in Gambia

Helminth and tick burdens of N'Dama cattle kept in village herds were compared with parasite burdens in Zebu cattle introduced into the same herds. The animals were monitored regularly for tick and helminth burdens, and blood samples were examined for differential white cell counts. The Zebu were found to have significantly higher numbers of endo- and ectoparasites. The N'Dama had significantly higher levels of circulating eosinophils than the Zebu during peak parasite burdens.

No difference in antibody levels to Amblyomma variegatum infestation could be detected between the two breeds. It is suggested that observed differences in susceptibility to endo- and ectoparasites between the two breeds cannot be totally attributed to environmental naivety of the Zebu, but must be partially owing to enhanced innate resistance factors in the N'Dama.