A genetic and immunological comparison of tick-resistance in beef cattle following artificial infestation with Rhipicephalus ticks.

Host resistance to ticks can be explored as a possible approach of combating tick infestations to complement the existing unsustainable tick control methods. Thirty-six beef cattle animals were used, consisting of Angus, Brahman and Nguni breeds, with each breed contributing 12 animals. Half of the animals per breed were artificially challenged with Rhipicephalus microplus and the other half with R. decoloratus unfed larvae per animal. Skin biopsies and blood samples were collected pre-infestation and 12 h post-infestation from the feeding sites of visibly engorging ticks. The success rate of the ticks was high and had an influence even at the early time point. Increased lymphocytes and blood urea nitrogen levels as well as decreased levels of segmented neutrophils were observed in the Angus, which were the opposite of those in the Brahman and Nguni. The increase in cholesterol, which was highest in the Angus and lowest in the Nguni, may be due to altered protein metabolism. The expression profiles of genes TRAF6, TBP, LUM and B2M were significantly different among breeds. Five genes (CCR1, TLR5, TRAF6, TBP, BDA20) had increased or constant expression post-infestation, whereas the expression of CXCL8, IL-10 and TNF-α decreased or remained the same after tick challenge. Genes that showed variation are involved in discouraging long-term supply of blood meal to the tick and those associated with immune responses. The gene LUM is a potential biomarker for tick resistance in cattle. The response to infestation by the breeds was consistent across the tick species.

In search of the Rhipicephalus (Boophilus) microplus in the western-central regions of the Eastern Cape Province, South Africa.

The southern cattle tick, Rhipicephalus (Boophilus) microplus, is an economically important tick that parasitises cattle and is found on other host species if they graze with cattle. The R. (B.) microplus is a highly adapted tick species prevalent in tropical and subtropical regions of the world. In Africa, it has expanded its range and was reported to supersede the native tick, R. (B.) decoloratus. The objective of the study was to determine the distribution of R. (B.) microplus under different ecological zones in the western-central regions of Eastern Cape Province. Engorged adult blue ticks were collected monthly from 360 randomly selected cattle and free living ticks from six replicate drags of the vegetation over a period of 1 year at Bedford Dry Grassland (BDG), Kowie Thicket (KT) and Bhisho Thornveld (BT). A special attention was paid to the lower perineum, neck, dewlap and ventral body parts which are the preferred sites for blue ticks during sampling. In this study, 9 species of ticks which grouped under 5 genera were identified. The identified species of ticks were Amblyomma hebraeum, Haemaphysalis elliptica, Hyalomma rufipes, Ixodes pilosus, R. (B.) decoloratus, R. appendiculatus, R. evertsi evertsi, R. follis and R. simus. Only adult R. (B.) decoloratus (n = 8090) ticks were collected from cattle between April 2016 and March 2017. A total of 4382 females and 3708 males of R. (B.) decoloratus were recovered during the survey. Of the ticks (n = 2885) collected from the vegetation, R. (B.) decoloratus was the most abundant species with a relative prevalence of 58.16%, followed by R. appendiculatus (18.37%) and R. evertsi evertsi (16.90%). Least abundant ticks were H. rufipes (2.98%), A. hebraeum (2.46%), H. elliptica (0.38%), R. follis (0.34%), I. pilosus (0.24%) and R. simus (0.17%). The distribution of R. (B.) decoloratus ticks differ significantly (P < 0.05) among the vegetation types. Significantly more (P < 0.05) engorged R. (B.) decoloratus were collected in KT during summer season (1.39 ± 0.063 females and 1.30 ± 0.063 males) compared to other vegetation types. The R. (B.) decoloratus larvae were significantly higher (P < 0.05) in BT (20.56±1.154) and KT (18.50±1.154) vegetation types during the spring season. R. (B.) microplus was not found in the present study, signifying that it is not yet established in western-central regions of the Eastern Cape Province and as such, continuous monitoring would be advisable.

Ecological preferences and seasonal dynamics of ticks (Acari: Ixodidae) on and off bovine hosts in the Eastern Cape Province, South Africa.

A total of 31,425 ticks were collected from 10 cattle and also from six drag-samples during the 12-month study period. Adult ticks were removed from the right hand side of each animal and all instars of ticks were placed in containers filled with 70% ethanol. Based on morphological traits, 10 tick species were identified: Rhipicephalus (Boophilus) decoloratus (32.5%), R. evertsi evertsi (18.8%), R. appendiculatus (17.3%), Amblyomma hebraeum (16.3%), R. simus (7.7%), Ixodes pilosus (3.8%), Hyalomma rufipes (3.5%), R. follis (0.08%), Haemaphysalis elliptica (0.04%), H. silacea (0.02%). The southern African yellow dog tick, H. elliptica, was only found on vegetation. The agro-ecological zones differ significantly in tick species and their distribution. The A. hebraeum and R. evertsi evertsi counts were higher in Kowie Thicket (KT) during summer season (2.05 ± 0.01 and 1.00 ± 0.09, respectively) compared to Bedford Dry Grassland (BDG) and Bhisho Thornveld (BT) veld types. In all vegetation types, R. appendiculatus had higher counts in KT in spring (0.91 ± 0.08), summer (0.78 ± 0.08) and winter (0.78 ± 0.08). Rhipicephalus (Boophilus) decoloratus was more frequent in the BT (1.78 ± 0.11) during the summer season. BDG had lower tick infestation with R. evertsi evertsi being the most frequent species in summer. No H. rufipes was collected in the KT. Of epidemiological interest, R. (B.) microplus was absent in the study area which needs further investigation. Within the context of this study, we found agro-ecological differences and seasonal variations to have influence on tick species distribution.

Cutaneous hypersensitivity responses to Rhipicephalus tick larval antigens in pre-sensitized cattle.

Nguni cattle are known to be more resistant to ticks than Bonsmara cattle, even if the immunological mechanisms responsible for this phenomenon are not fully understood. Cutaneous hypersensitivity responses to unfed larval extracts (ULE) of the ticks Rhipicephalus decoloratus and Rhipicephalus microplus were investigated in Nguni and Bonsmara cattle to improve knowledge on the immunity to ticks. Hypersensitivity reactions were induced by intradermal inoculation of 0.1ml of ULE of R. decoloratus and R. microplus ticks (50µg protein) in the right and left ear, respectively, of 8-9-month-old Nguni (n=11) and Bonsmara (n=9) heifers. Ear thickness was measured using callipers before and 0.5, 1, 6, 24, 48, and 72h post inoculation (PI). Bonsmara cattle showed a more intense immediate reaction with maximum response at 1h PI and no delayed hypersensitivity reaction. Nguni heifers, conversely, presented a less intense immediate reaction with maximum response at 1h PI, and a delayed hypersensitivity reaction at 72h PI. Reactions to R. decoloratus ULE produced a more intense skin response than to R. microplus in both breeds at all time intervals. Nguni cattle showed lower tick infestation indicating higher tick resistance than Bonsmara cattle. Delayed hypersensitivity reaction could be associated with superior tick resistance in the Nguni breed, while immediate hypersensitivity reaction could be associated with increased tick susceptibility in the Bonsmara breed. This study indicates the need for further investigations on the correlation of tick resistance and cellular immune responses to tick infestation in Nguni cattle.

Stress reactivity and its relationship to beef quality in Nguni steers supplemented with Acacia karroo leaves.

The objective of this study was to determine the levels of catecholamines and their relationship to beef quality in Nguni steers fed on Acacia karroo leaves. A total of 30 19-month-old steers were randomly assigned to A. karroo leaves (AK), sunflower cake (SF) and the control with no supplement (CN) diets. The AK and SF diets provided the steers with an additional 150 g of protein per day for 60 days. Catecholamine levels were determined from urine samples collected from each steer before and after slaughter. The Musculus longissimus thoracis et lumborum was sampled for selected meat quality measurements. Nguni steers on the CN diet had higher (P < 0.05) concentrations of post-mortem urinary norepinephrine and dopamine compared with those that received the AK and SF diets. Norepinephrine was negatively linearly related (P < 0.05) to the Warner-Bratzler shear force value of meat aged for 21 days and cooking loss of meat aged for 2 days (CL2) in steers that were given the SF diet. Meat pH and drip loss values were inversely related (P < 0.05) to epinephrine concentration in steers that received the AK diet. Dopamine concentration was negatively linearly related (P < 0.05) to water holding capacity and CL2 for steers on the CN diet. For steers on the CN diet, lightness (L*) values increased (P < 0.05) with increase in dopamine concentration. It was concluded that stress responsiveness and its relationship to certain beef quality attributes could be positively manipulated by supplementation with A. karroo leaves.

Ovarian activity, conception and pregnancy patterns of cows in the semiarid communal rangelands in the Eastern Cape Province of South Africa.

A study was conducted to determine the seasonal trends in ovarian activity, conception and pregnancy status of cows on communal rangelands in the Eastern Cape Province of South Africa. Ovarian activity and pregnancy status of 200 cows were determined through trans-rectal palpation in June, and October 2007 and January 2008. Month of conception was obtained by subtracting the estimated age of the foetus from the month when pregnancy diagnosis was performed. Body weights and body condition scores (BCS) were collected every month between March 2007 and January 2008. Although cows in the perennial grasslands had higher (P<0.05) body weights and BCS than those in the annual grasslands, they had a significant weight and condition loss between March and October. More than 90% of the cows in the annual grasslands were cycling in January (P<0.05). Over 60% of the cows in the perennial grasslands conceived between December and March compared to 46% in the annual grasslands. About 40% of the cows were pregnant in June in the annual and perennial grasslands. There were more cycling and pregnant cows with a BSC of 3 in the perennial grasslands in June and October compared to annual grasslands (P<0.05). Odds ratio estimates of cows exhibiting ovarian activity and pregnancy in the communal areas were highest for BCS. It was concluded that most cows conceived and exhibited ovarian activity between November and March, especially in the perennial grasslands. Future research should focus on supplementary feeding using locally available feed resources to improve cow reproductive performance in the dry months, particularly in the annual grasslands.