The comparison of immunological responses of Brahman, Nguni and Angus cattle infested with Rhipicephalus microplus and Rhipicephalus decoloratus

Nel, Cornelius Loftus (2017-03)

Thesis (MScAgric)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Ticks and tick borne diseases pose major threats to modern South African cattle production. Rhipicephalus microplus and R. decoloratus are important tick species currently spread throughout most of Southern Africa. Current control methods are not considered sustainable because of various economic, social and environmental concerns. Host resistance to ticks is a characteristic of cattle and is dependent on breed type. An understanding of these resistance mechanisms is necessary if host resistance is to be exploited as an alternative control method. Host reaction to infestation is specific to the tick species. It was hypothesized that tick resistance is a product of co-evolution between host and parasite and a breed will thus show superior resistance to tick species that it has a historical relationship with. The parasite-host pair with African origin, R. decoloratus and the Bos taurus africanus Nguni, was thus chosen along with the pair of Asiatic origin, R. microplus and the Bos indicus Brahman. A European breed, the Bos taurus Angus was also included due to their known susceptibility to Rhipicephalus ticks. Following the collection of control samples on all animals (n=36), one half (n=6) of breed group (n=12) was artificially infested with roughly 100 unfed larvae of R. microplus while the other half was similarly infested with R. decoloratus. Approximately 12 hours’ post infestation, multiple blood samples were drawn and skin biopsy samples were collected from visible parasitized sites of all animals. The remaining ticks were allowed to mature and tick counts were performed on day 18 post infestation. The blood samples were used for comprehensive haematology and serum biochemistry profiles while the skin biopsy sites were sectioned for cell counts and histopathological scoring of tissue using hematoxylin and eosin staining. There was no significant interaction between breed and tick species for counts, haematology, biochemistry or cutaneous cell counts and breed and tick species was used as fixed effects for assessment. Regarding day 18 tick counts, the Brahman breed displayed lower (p<0.01) tick counts compared to both the Nguni and Angus breeds. Rhipicephalus microplus displayed a higher success rate (p<0.05) compared to R. decoloratus across all breeds. At the 12-hour time point, the Brahman breed displayed a lower (p<0.05) level of mean cell volume (40.94 fl). The Nguni breed displayed a lower (p<0.05) level of platelets (311.59 x 109/dl). No haematological differences were observed for tick species. The Angus breed displayed a lower (p<0.05) absolute level of circulating neutrophils (3.65 x 109/l) and a higher (p<0.05) level of lymphocytes (9.69 x 109/l) compared to the Nguni, but not Brahman breed. The Nguni displayed a higher (p<0.05) absolute level of eosinophils (0.43 x 109/l) compared to the Brahman, but not Angus breed. Regarding serum biochemistry, the Brahman breed displayed higher (p<0.05) albumin levels (28.85 g/l) compared to both breeds and higher (p<0.05) alanine transferase (59.70 U/l) levels compared to the Angus breed. The Angus breed displayed higher (p<0.05) levels of blood urea nitrogen (5.21 mmol/l) compared to the Brahman breed. The Brahman breed displayed lower levels of fibrinogen (1.77 g/l) than the Nguni and Angus breeds. Animals infested with R. microplus displayed a higher (p<0.05) serum globulin level (43.37 g/l) than those infested with R. decoloratus. Overall, alanine transferase (-0.36, p<0.05), alkaline phosphatase (-0.36, p<0.05) and fibrinogen (0.39, p<0.05) showed weak, but significant correlations to day 18 tick counts. No differences within breed and tick species groups were observed within the number of cellular infiltrates or histopathology scores. Within all treatment groups, the level recorded for cutaneous infiltrates or histopathology scores post infestation was higher (p<0.05) than the control values. It was concluded that a specific evolutionary relationship is not necessarily the primary contributor to the manifestation of the resistant phenotype and a high level of cross resistance is possible. R. microplus has a superior parasitic aggression which will have an influence on its displacement of R. decoloratus. Immunological parameters are important when assessing tick-host relationships, but the influence on the host includes a wider range of factors. The 12-hour interval is promising for further investigations, but higher intensities of infestation are recommended to increase the reliability of assessments.

AFRIKAANSE OPSOMMING: Bosluise en bosluis-oordraagbare siektes hou groot bedreigings vir moderne Suid-Afrikaanse vee produksie in. Rhipicephalus microplus en Rhipicephalus decoloratus is belangrike bosluisspesies tans versprei deur die grootste gedeeltes van Suider-Afrika. Huidige beheermaatreëls word nie as volhoubaar beskou nie as gevolg van verskeie ekonomiese, maatskaplike en omgewingskwessies. Weerstand teen bosluise is 'n kenmerk van beeste en is afhanklik van ras. 'n Begrip van die meganismes van weerstandigheid is nodig as gasheer weerstand uitgebuit gaan word as 'n alternatiewe metode van beheer. Die gasheer reaksies op infestasie is spesifiek teen opsigte van die bosluis spesie. Dit is gevolglik vermoed dat bosluis weerstandigheid 'n produk is van ko-evolusie tussen gasheer en parasiete. Rasse sal dus moontlik ‘n beter weerstand fenotiepe wys tot bosluis spesie met wie dit 'n historiese verhouding deel. Die parasiet-gasheer paar met Afrikaanse herkoms, R. decoloratus en die Bos taurus africanus Nguni, was dus gekies saam met die paar van Asiatiese oorsprong, R. microplus en die Bos indicus Brahman. 'n Europese ras, die Bos taurus taurus Angus, is ook ingesluit as gevolg van hul bekende vatbaarheid vir bosluise. Na die versameling van kontrole monsters op alle diere (N = 36), was een helfte (N = 6) van elke ras groep (N = 12) kunsmatig geïnfesteer met sowat 100 ongevoerde larwes van R. microplus terwyl die ander helfte op ‘n eenerse wyse geïnfesteer is met R. decoloratus. Ongeveer 12 ure na besmetting is verskeie bloedmonsters getrek en vel biopsie monsters is versamel van sigbare areas van infestasie. Die oorblywende bosluise was toegelaat om tot volwassenheid te ontwikkel en bosluis tellings is uitgevoer op dag 18 (na infestasie). Die bloedmonsters is gebruik vir omvattende hematologie en serum biochemie profiele terwyl die vel biopsies gesny is vir seltellings en histopatologiese evaluasie van weefsel met behulp van hematoxylin en eosin toepassing. Interaksie tussen ras en bosluisspesie was nie betekenisvol vir bolsuis tellings, hematologie, biochemie of kutane seltellings nie. Hoof effekte ras en bosluisspesie is dus oorweeg vir assessering. Met betrekking tot dag 18 bosluis tellings, het die Brahman ras laer (p <0,01) tellings in vergelyking met beide die Nguni en Angus rasse vertoon. R. microplus het 'n hoër suksessyfer (p<0.05) in vergelyking met R. decoloratus oor alle rasse vertoon. Op die 12-uur-tyd punt, het die Brahman ras 'n laer (p<0.05) vlak van die gemiddelde sel volume (40,94 fl) vertoon. Die Nguni-ras het 'n laer (p<0.05) vlak van plaatjies (311,59 x 109/dl) vertoon. Geen hematologie verskille is waargeneem vir tussen bosluis spesies nie. Die Angus ras het ‘n laer (p <0.05) absolute vlak van sirkulerende neutrofiele (3,65 x 109/l) en 'n hoër (P <0,05) vlak van limfosiete (9,69 x 109/l) vertoon in vergelyking met die Nguni, maar nie Brahman ras. Die Nguni het 'n hoër (p<0,05) absolute vlak van eosinofiele (0,43 x 109/l) in vergelyking met die Brahman, maar nie die Angus ras, vertoon. Met betrekking tot serum biochemie, het die Brahman ras hoër (p<0,05) albumien vlakke (28,85 g/l) in vergelyking met beide rasse vertoon en hoër (p<0,05) alanien transferase (59,70 U/l) vlakke in vergelyking met die Angus ras vertoon. Die Angus ras het hoër (P <0.05) vlakke van bloed ureum stikstof (5.21 mmol/l) in vergelyking met die Brahman ras vertoon. Die Brahman ras vertoon laer vlakke van fibrinogeen (1.77 g/l) as die Nguni en Angus rasse. Diere wat geïnfesteer is met R. microplus het hoër (P <0,05) serum globulien vlakke (43,37 g/l) geïnfesteer as dié besmet is met R. decoloratus. Algeheel, het alanien transferase (-0,36, p<0.05), alkaliese fosfatase (-0,36, p<0.05) en fibrinogeen (0,39, p<0.05) swak, maar betekenisvolle korrelasies getoon teenoor dag 18 bosluis tellings. Geen verskille tussen ras of bosluisspesies groepe is waargeneem in die aantal inflammatoriese seltellings of histopatologie tellings nie. Binne alle behandeling groepe, het die vlak vir kutane seltellings en histopatologiese tellings hoër (p<0,05) as die kontrole waardes. Daar is tot die gevolgtrekking gekom dat 'n spesifieke evolusionêre verhouding is nie noodwendig die primêre bydraer was tot die manifestasie van die weerstandige fenotipe nie en 'n hoë vlak van kruis weerstand is moontlik. R. microplus het 'n verhoogde parasitiese aggressie wat 'n invloed op sy verplasing van R. decoloratus sal hê. Immunologiese eienskappe is belangrik vir die ondersoek van bosluis-gasheer verhoudings, maar die invloed van infestasie op die gasheer sluit 'n wyer verskeidenheid van faktore in. Die 12 uur interval is belowend vir verdere ondersoeke, maar hoër intensiteite word aanbeveel om die betroubaarheid van assessering te verhoog.

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