11 research outputs found
Aspects of the epidemiology of Theileria parva infections in cattle and African buffalo (Syncerus caffer) in South Africa revealed by tick transmission and sub-inoculation of blood
The aim of this study was to investigate three key epidemiological aspects of Theileria parva infections in cattle and African buffalo (Syncerus caffer) in South Africa. The first of these was the possible behavioural change (i.e. transformation) of buffalo-derived T. parva (causing classical Corridor disease in cattle) to what might be considered cattle-derived T. parva (causing classical East Coast fever in cattle) after repeated tick-passage in cattle. For the first time a South African isolate of buffalo-derived T. parva was successfully transmitted using Rhipicephalus zambeziensis for eight passages in non-splenectomised cattle. This was achieved despite most animals developing fatal infections with extremely low piroplasm parasitaemias, and without chemotherapeutic intervention. This finding indicates that, contrary to earlier belief, Corridor disease is not a self-limiting disease in cattle, and given the opportunity, could well become established in a cattle population in the absence of buffalo. Despite repeated tick transmission in cattle of the South African buffalo isolate of T. parva used in this study, it did not exhibit the behavioural changes associated with âtransformationâ to typical cattle-derived T. parva. Secondly, the potential role of the common waterbuck (Kobus ellipsiprymnus) in the selection of cattle-adapted subpopulations of parasites from buffalo-derived T. parva was investigated. Waterbuck captured in Kruger National Park (KNP) were screened by conventional and molecular diagnostic techniques for Theileria spp. infections. Laboratory-reared R. zambeziensis were fed on captive buffalo confirmed to be naturally infected with T. parva. The ensuing adult ticks were fed on captive waterbuck and cattle. All the waterbuck were found to carry microscopically detectable Theileria sp. piroplasm infections, found by polymerase chain reaction (PCR) diagnosis to belong to a hitherto uncharacterised Theileria species. R. zambeziensis adults which fed as nymphs on the buffalo transmitted fatal T. parva infections to cattle. However, no transmission of T. parva to the waterbuck could be demonstrated clinically or by PCR diagnosis. Also, R. zambeziensis nymphs that were subsequently fed on the waterbuck failed to transmit T. parva to cattle in the ensuing adult stage, confirming the absence of T. parva-group infections in the waterbuck. The results suggest that buffalo in KNP probably do not carry T. parva-group parasites which are readily transmissible to common waterbuck and waterbuck are therefore unlikely to play an important role in the epidemiology of T. parva-group infections in cattle in South Africa. Thirdly, to investigate the carrier state of buffalo-derived T. parva infections in cattle, blood from infected non-splenectomised and splenectomised carrier cattle was subinoculated to splenectomised cattle. T. parva infections were successfully transmitted by subinoculation of 1000 ml of blood at various intervals after infection to splenectomised recipient cattle. Donor animals comprised of recovered intact cattle, reacting intact cattle or splenectomised recovered cattle. Microscopically detectable piroplasm parasitaemias were detected in all recipients after inoculation. One splenectomised recipient developed a moderate clinical reaction, accompanied by a moderate schizont parasitosis, but recovered spontaneously, confirming persistence of schizonts in some T. parva carrier animals. By contrast, a T. parva piroplasm infection, persisting in a treated recovered splenectomised bovine, in the apparent absence of circulating schizonts, was serially (consecutively) passaged in splenectomised cattle. Seroconversion occurred in all recipient cattle. With the exception of the recipient which developed a clinical reaction and circulating schizonts, none of the recipients showed any clinical signs of T. parva infection. Upon homologous sporozoite challenge with T. parva, two out of three recipient animals with only microscopically detectable piroplasm parasitaemias developed fatal T. parva infections and one recovered after exhibiting severe clinical signs. These findings confirm the stage-specific immunity in T. parva and, contrary to popular belief, the possibility of long-term maintenance of piroplasm parasitaemias in the absence of schizonts in carrier cattle. The technique of subinoculating and establishing virulent T. parva carrier infections in splenectomised cattle also provides a method whereby buffalo-derived parasite stocks may be isolated and maintained for characterisation and the preparation of sporozoite stabilates for inclusion in T. parva vaccines. CopyrightDissertation (MSc)--University of Pretoria, 2011.Veterinary Tropical Diseasesunrestricte
Comparative infection rates of Theileria parva lawrencei in salivary glands of Rhipicephalus appendiculatus and Rhipicephalus zambeziensis
Three cattle, which had been experimentally infected with Theileria parva lawrencei and maintained
as carriers of the infection, were each infested simultaneously with clean nymphal Rhipicephalus appendiculatus
and Rhipicephalus zambeziensis in ear bags on separate ears. After moulting, the ensuing adult
ticks were fed on rabbits for 4 days and their salivary glands were examined for infective stages of the
parasite. Microscopic examination revealed significantly higher infection rates in the salivary glands of
R. zambeziensis than in R. appendiculatus which may indicate an increased vector efficiency of R.
zambeziensis for T. p. lawrencei.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201
Theileriosis (Cytauxzoonosis) in Roan antelope (Hippotragus equinus) : field exposure to infection and identification of potential vectors
Four hand-reared, naĂŻve roan antelope, 4 months of age, were exposed to naturally infected
pasture on a game farm in Mpumalanga Province, South Africa, where roan are known
to die from theileriosis. Various clinical parameters were recorded during this period.
The predominant ticks parasitising these animals at the time (January to February), were
Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi adults. After a period of 5 weeks
the animals developed signs of clinical theileriosis and were treated with buparvaquone to
prevent mortality. Primary hyperplasia of the local draining lymph nodes (Lnn. anorectales)
near the feeding site of adult R. evertsi evertsi indicated possible transmission of Theileria sp.
(sable) by this tick species. After recovery from theileriosis, these animals were confirmed
carriers of Theileria sp. (sable) by PCR (polymerase chain reaction) and DNA probe analysis.
Laboratory-bred larvae and nymphs of R. evertsi evertsi and R. appendiculatus respectively,
were fed on the ears of these roan antelope. Salivary glands from moulted and prefed adult
ticks of each species were dissected and stained for Theileria spp., and the PCR and DNA
probe applied to a representative batch of dissected glands. R. appendiculatus adults collected
from grass in infected camps were also dissected after prefeeding them on rabbits. Salivary
glands of both tick species showed infected acini on staining and were also positive for
Theileria sp. (sable) only, on multiprotozoal PCR-screening analysis. There was no statistical
significant difference between the infection rate and the intensity of infection between the
two tick species. R. appendiculatus ticks collected from grass were also PCR-positive for
Theileria sp. (sable).Mr J. Hume, owner of
Mauricedale Game Ranch.http://www.ojvr.orgmn201
An investigation into alternative methods for the diagnosis of dourine
The complement fixation test (CFT), indirect fluorescent antibody test (IFAT), card agglutination test for trypanosomiasis (CATT) and enzyme-linked immunosorbent assay (ELISA) were compared in their application to the serological diagnosis of Trypanosoma equiperdum infection in 43 horses. The CFT remains a reliable test for dourine, especially in countries where other members of the subgenus Trypanozoon do not occur. The IFAT is a Good 'back-up' test, but, requiring skilled operators it has the disadvantage of making it labour intensive, and interpretation of results subjective. This makes it more suited to small numbers of samples. The ELISA is suitable for large numbers of samples and could readily be used in routine diagnostic procedures. The CATT could be of value in field situations, although it does not appear to be as sensitive as the CFT. Its possible application under these conditions should be further investigated.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201
A survey of the incidence and importance of the tick-borne diseases heartwater, redwater and anaplasmosis in the heartwater-endemic regions of South Africa
In an almost 50% response to a survey questionnaire, farmers in the heartwater-endemic regions of South Africa indicated that they were experiencing losses of 1,3, 0,3 and 0,2% in cattle due to heartwater, redwater and anaplasmosis, respectively. In small stock, the heartwater mortality was 3,8%. Only 35% of cattle farmers and 15% of farmers keeping sheep and goats, vaccinate their animals against heartwater. It would seem that the present vaccine does not control heartwater adequately and, with 9% of farmers claiming poor protection after immunization, it would be difficult to recommend wider use of the heartwater vaccine. Likewise, vaccination against redwater and anaplasmosis on 11,8 and 14,2% of farms, respectively, appears to have had no beneficial effect on the mortality rates of these diseases. Many farmers still believe that very few or no ticks should be seen on cattle. In fact, it would appear that a considerable proportion of farmers find so few ticks on their cattle, that the frequency of acaricidal treatment is in many cases too high. Although there is no correlation between the incidence of heartwater and the intensity of tick control, there is also no serological evidence to support the possibility of an endemically unstable condition. The concept that endemic stability as a means to control heartwater in cattle can be achieved by allowing more ticks on animals, has not yet been established. The overall impression is that farmers do not regard heartwater in cattle as such a serious problem as it is generally believed to be. In small stock, however, heartwater is a severe constraint in the bushveld regions of the Transvaal and in the valley bushveld of the eastern Cape Province. In the latter, it is particularly Angora goats that are affected.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201
Evidence of lumpy skin disease virus over-wintering by transstadial persistence in Amblyomma hebraeum and transovarial persistance in Rhipicephalus decoloratus ticks
Lumpy skin disease is a debilitating cattle disease caused by the lumpy skin
disease virus (LSDV), belonging to the genus Capripoxvirus. Epidemics of the disease
usually occur in summer, when insect activity is high. Limited information is available on
how LSDV persists during inter-epidemic periods. Transmission of LSDV by mosquitoes
such as Aedes aegypti has been shown to be mechanical, there is no carrier state in cattle
and the role of wildlife in the epidemiology of the disease seems to be of minor importance.
Recent studies in ticks have shown transstadial persistence of LSDV in Rhipicephalus
appendiculatus and Amblyomma hebraeum as well as transovarial persistence of
the virus in Rhipicephalus decoloratus, R. appendiculatus and A. hebraeum. The overwintering
of ticks off the host as part of their life cycles is well known: A. hebraeum and
R. appendiculatus over-winter, for example, on the ground as engorged nymphs/unfed
(emergent) adults while R. decoloratus over-winters on the ground as engorged females. In
this study, transstadial and transovarial persistence of LSDV from experimentally infected
A. hebraeum nymphs and R. decoloratus females after exposure to cold temperatures of
5 C at night and 20 C during the day for 2 months was reported. This observation
suggests possible over-wintering of the virus in these tick species.Combating Infectious Diseases of Livestock for International Development (CIDLID) research programme, the Department of International Biotechnology and Biological Sciences Research Council (BBSRC), the UK government, the Department for International Development (DFID) and the Scottish Government (CIDLID Project
Number BB/H009361/1).http://link.springer.com/journal/10493hb201
Improved detection of Babesia bigemina from various geographical areas in Africa using quantitative PCR and reverse line blot hybridisation
Babesia bigemina is one of the aetiological agents of bovine babesiosis, which causes economic losses through mortality, loss of production and control costs. Effective means of detecting and quantifying B. bigemina in cattle populations is therefore important to inform control approaches. In order to examine the parasite genetic diversity in African countries, B. bigemina 18S rRNA genes from cattle from South Africa, Uganda and Angola were sequenced. The 25 distinct B. bigemina 18S rRNA gene sequences obtained in this study showed 99 to 100% identity with previously published sequences of strains from African and other continents. The sequences of the previously published B. bigemina 18S rRNA gene-specific quantitative PCR (qPCR) primers and probe, developed based on American and Asian strains, were conserved in the African B. bigemina sequences. The qPCR assay was evaluated using 10-fold and 2-fold serial dilutions of B. bigemina-infected erythrocytes to determine the efficiency and analytical sensitivity. The qPCR assay had an efficiency of 98.14 ± 1.71%, and the limit of detection was approximately 1.5 infected red blood cells (iRBCs) per microlitre (Όl) of blood. The detection rate of B. bigemina from duplicates of field-collected blood samples from cattle from South Africa, Mozambique and Angola was 37% (30/81), 12% (6/49) and 50% (38/76), respectively. Reverse line blot hybridisation (RLB) results obtained from the same samples in previous studies, using a previously published B. bigemina-specific probe, detected the parasite DNA in only 1.5% (3/206) of the samples. A new B. bigemina-specific RLB oligonucleotide probe was designed in the hypervariable V4 region of the 18S rRNA gene. Screening of field blood samples from cattle showed that the new probe was specific, and its frequency of detection of B. bigemina was three times higher than the previously published probe. The qPCR assay and the newly developed B. bigemina-specific RLB probe provide good tools for epidemiological studies, which are essential in the control of bovine babesiosis.The Health and Welfare Sector Education and Training Authority (HWSETA), the Belgian Directorate General for Development Co-operation (DGCD) Framework agreement ITM/DGCD and the Claude Leon Foundation of South Africa.http://www.elsevier.com/locate/ttbdishj2021Veterinary Tropical Disease
Genetic diversity, acaricide resistance status and evolutionary potential of a Rhipicephalus microplus population from a disease-controlled cattle farming area in South Africa
The Southern cattle tick, Rhipicephalus microplus is a hematophagous ectoparasite of great veterinary and economic importance. Along with its adaptability, reproductive success and vectoring capacity, R. microplus has been reported to develop resistance to the major chemical classes of acaricides currently in use. In South Africa, the Mnisi community in the Mpumalanga region offers a unique opportunity to study the adaptive potential of R. microplus. The aims of this study therefore included characterising acaricide resistance and determining the level and pattern of genetic diversity for R. microplus in this region from one primary population consisting of 12 communal dip-stations. The level of acaricide resistance was evaluated using single nucleotide polymorphisms (SNPs) in genes that contribute to acaricide insensitivity. Additionally, the ribosomal internal transcribed spacer 2 (ITS2) gene fragments of collected individuals were sequenced and a haplotype network was constructed. A high prevalence of alleles attributed to resistance against formamidines (amitraz) in the octopamine/tyramine (OCT/Tyr) receptor (frequency of 0.55) and pyrethroids in the carboxylesterase (frequency of 0.81) genes were observed. Overall, the sampled tick population was homozygous resistant to pyrethroid-based acaricides in the voltage-gated sodium channel (VGS) gene. A total of 11 haplotypes were identified in the Mnisi R. microplus population from ITS2 analysis with no clear population structure. From these allele frequencies it appears that formamidine resistance in the Mnisi community is on the rise, as the R. microplus populations is acquiring or generating these resistance alleles. Apart from rearing multi-resistant ticks to commonly used acaricides in this community these ticks may pose future problems to its surrounding areas.Zoetis (Pty) Ltd., South Africa, the National Research Foundation Technology and Human Resources for Industry Programme (Grant number TP12082911252) and the Belgium Development Cooperation (DGD) FA3 project.http://www.elsevier.com/locate/ttbdis2017-06-30hb2016GeneticsVeterinary Tropical Disease
Mechanical transmission of lumpy skin disease virus by Rhipicephalus appendiculatus male ticks
Lumpy skin disease (LSD) is an economically important, acute or sub-acute, viral disease of
cattle that occurs across Africa and in the Middle East. The aim of this study was to investigate if
lumpy skin disease virus (LSDV) can be transmitted mechanically by African brown ear ticks
(Rhipicephalus appendiculatus Neum.). Laboratory-bred R. appendiculatus males were fed on
experimentally infected viraemic âdonorâ cattle. Partially fed male ticks were then transferred to
feed on an uninfected â recipient â cow. The recipient animal became viraemic, showed mild clinical
signs of LSD and seroconverted. Additionally, R. appendiculatus males were found to transmit
LSDV through feeding on skin lacking visible lesions, demonstrating that viraemic animals
without lesions at the feeding site of ticks may be a source of infection. This is the first time that
transmission of poxviruses by a tick species has been demonstrated and the importance of this
mode of transmission in the spread of LSDV in endemic settings is discussed.Combating Infectious Diseases
of Livestock for International Development
(CIDLID) research programme, the Department of
International Biotechnology and Biological Sciences
Research Council (BBSRC), the UK Government, the Department for International Development
(DFID) and the Scottish Government (CIDLID
project no. BB/H009361/1).http://journals.cambridge.org/action/displayJournal?jid=HYGam2013ab201
Demonstration of lumpy skin disease virus infection in Amblyomma hebraeum and Rhipicephalus appendiculatus ticks using immunohistochemistry
Lumpy skin disease (LSD) is caused by lumpy skin disease virus (LSDV), a member of the genus
Capripoxvirus. Transmission of the virus has been associated with haematophagous insects such as Stomoxys
calcitrans as well as Aedes and Culex species of mosquitoes. Recent studies have reported the
transmission of the virus by Amblyomma hebraeum, Rhipicephalus appendiculatus, and Rhipicephalus decoloratus
ticks and the presence of LSDV in saliva of A. hebraeum and R. appendiculatus ticks. The aim of this
study was to determine which tick organs become infected by LSDV following intrastadial infection and
transstadial persistence of the virus in A. hebraeum and R. appendiculatus ticks. Nymphal and adult ticks
were orally infected by feeding them on LSDV-infected cattle. Partially fed adult ticks were processed for
testing while nymphs were fed to repletion and allowed to moult to adults before being processed for
testing. The infection in tick organs was determined by testing for the presence of the viral antigen using
monoclonal antibodies with immunohistochemical staining. The viral antigen was detected in salivary
glands, haemocytes, synganglia, ovaries, testes, fat bodies, and midgut. Since the virus was shown to be
able to cross the midgut wall and infect various tick organs, this may indicate potential for biological
development and transmission of LSDV in ticks. This study strengthens the previously reported evidence
of the occurrence of LSDV in tick saliva.http://www.elsevier.com/locate/ttbdishb2014ab201