Thesis (MSc (Veterinary Tropical Diseases, Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

Thesis (M.S.)--University of Missouri--Columbia, 2004. / Typescript. Includes bibliographical references (leaves 35-38). Also issued on the Internet.

This study was conducted to understand the occurrence, diversity and epidemiology of tickborne diseases (TBDs) in a transhumant pastoral area of Karamoja Region, Uganda. We used participatory epidemiology (PE), involving focus group discussions (n = 24) with livestock keepers, 30 key informant interviews, review of previous surveillance data, clinical examinations, and laboratory confirmation of cases of TBDs, to define and prioritise cattle diseases, evaluate current control activities, and identify constraints to the control of TBDs. The livestock keepers regarded TBDs, particularly East Coast fever (ECF) and anaplasmosis, as the most important health problems in their cattle, based on morbidity and mortality rates, rates of transmission, treatment costs, difficulty in accessing the correct treatment, difficulty to control, and inadequate knowledge to manage the diseases. The main constraints to the control of TBDs were inadequate knowledge, inadequate veterinary services and limited availability of drugs. Hand picking of ticks was done by all pastoralists while hand spraying was done with under-strength acaricides, often at irregular intervals and with little acaricide wash. We determined the endemic status of TBDs in 20 randomly-selected cattle herds by estimating the proportion of annual ECF and anaplasmosis cases in different age groups of cattle using participatory approaches and clinical examinations, determining the diversity and abundance of ticks (161 cattle in 20 herds), and establishing the seroprevalence of antibodies to Theileria parva and Anaplasma marginale among cattle (n = 397 in 20 herds). Clinical examinations and informant interviews showed that TBDs affected all age groups of cattle. Two-thirds of the cattle were infested with moderate (37.3%, 11-50 ticks) to abundant (28.6%, > 50 ticks) numbers of ticks. Out of the 10,923 ticks collected, Rhipicephalus appendiculatus (54.4%) was the most abundant species followed by R. decoloratus (17.7%), Amblyomma variegatum (12%) and A. lepidum (11.6%). We collected tick species that are either rare in Uganda (A. lepidum, Hyalomma truncatum, A. gemma) or were not known to be present in the country (R. pulchellus). The true seroprevalence of antibodies to A. marginale was high (95.1%, 95% confidence interval [CI] 91.3% - 98.5%), while that of T. parva was low (16.5%, 95% CI 12.9% - 19.6%). We determined the presence of tick-borne haemoparasites among cattle and the prevalence of infections using reverse line blot (RLB) hybridisation and quantitative real-time polymerase chain reaction (qPCR), and characterised Theileria and Babesia species by sequence and phylogenetic analyses of the full-length 18S rRNA gene. The RLB hybridisation assay demonstrated the presence of tick-borne haemoparasites in most cattle (99.6%), mostly as mixed infections (97.5%). The most frequently-detected species were Theileria mutans (88.3%, 95% CI: 84.6-92.1%), A. marginale (73.8%: 68.3-79.2%), T. velifera (71.3%: 65.8-76.7%) and Anaplasma sp. Omatjenne (63.3%: 57.5-68.8%). Other virulent pathogens, namely Babesia bigemina (5.0%) and T. parva (2.9%), were also detected with RLB, but Ehrlichia ruminantium was not detected. The proportions of qPCR positive samples were 82.9% (A. marginale), 12.1% (A. centrale), 3.3% (T. parva), and 1.7% (E. ruminantium). Variations (5 to 9 nucleotides) in the 18S rRNA gene sequences of B. bigemina were identified as compared with previously published sequences. We assessed the 16S rRNA gene phylogeny of Anaplasma species from cattle and analysed the msp1α gene sequences of A. marginale to identify genotypes. There was genetic heterogeneity within A. marginale in cattle in the study area. Most A. marginale sequences (16/19) were closely related (99- 100% identities) and clustered with A. marginale strain Veld from cattle in South Africa, with strong bootstrap support, while three sequences clustered (100% identity) with A. marginale strain from Virginia, USA. The A. centrale sequences were closely related (100% identity) and clustered with the Israel vaccine strain. We found four different kinds of MSP1a tandem repeat sequences (UP39-F-M2-3) that correspond to one A. marginale strain unique to Uganda. One tandem repeat (UP39) was unique to Karamoja cattle. The findings from this study provide knowledge on the diversity and epidemiology of TBDs, which can be used to support diagnosis and strategic control of TBDs, and consequently improve cattle productivity and the livelihoods of pastoralists. More effective control and prevention measures against ticks and TBDs should urgently be implemented in the region. There is need to facilitate and promote immunisation of cattle against ECF. Given the scarcity of veterinarians in the region, the activities of community-based animal health workers [CAHWs] should be strengthened. The local governments in Karamoja Region should facilitate a more favourable business environment to attract private companies, who could scale-up veterinary drug supplies to the region. Pastoralists should be sensitised to improve their ecological knowledge of the seasonal activity of ticks for strategic tick control. / Thesis (PhD)--University of Pretoria, 2017. / Agricultural Technology and Agribusiness Advisory Services (ATAAS) / The National Agricultural Research Organisation (NARO) of Uganda / Veterinary Tropical Diseases / PhD / Unrestricted

Three studies relating to the vector competency of several species of ticks and <i>Simulium</i> spp. (blackflies) for <i>Ehrlichia risticii</i>, causative agent of Potomac horse fever (PHF) and <i>Amblyomma variegatum</i> for <i>Cowdria ruminantium</i>, causative agent of heartwater, are described. <i>Dermacentor variabilis, Rhipicephalus sanguineus, Amblyomma americanum and Ixodes scapularis</i> ticks were investigated for their ability to acquire and transmit PHF. Larval and nymphal ticks were exposed to <i>E. risticii</i> by feeding on mice inoculated with the organism. Molted exposed ticks were then allowed to feed on susceptible ponies or mice and were examined by light and electron microscopy. No evidence of transmission, either clinically or by seroconversion in mice or ponies was observed. Blackflies (<i>Simulium</i> spp.) were trapped in an area endemic for PHF and inoculated into mice in an attempt to demonstrate <i>I. risticii</i>. No evidence of seroconversion by mice to <i>E. risticii</i> was observed. Two laboratory colonies of <i>Amblyomma variegatum</i> ticks were investigated for their ability to acquire and transmit C. <i>ruminantium</i> and was febrile. Nymphs from both laboratory groups were simultaneously fed on a goat that had been infected with C. <i>ruminantium</i> and was febrile. Engorged nymphs from both groups were replete from feeding on three consecutive days. Nymphs from both groups were then incubated under identical conditions until molting. / Ph. D.

Leishmaniasis is a parasitic disease that affects humans and animals in more than 98 countries across the globe placing more than 1 billion people at risk for the disease and killing more than 20,000 people per year. In the United States the disease is enzootic within the hunting dog population and vertical transmission has been identified as the primary route of transmission in this population. In Brazil the disease is endemic in the human population and enzootic in the dog population with vector and vertical transmission having been reported. In many diseases reports have found there is increased disease severity when an individual is co-infected with another organism. Case reports have suggested this may also occur with tick borne diseases and leishmaniosis in dogs but there is limited longitudinal data to support this relationship. Even less is known and understood regarding the risk factors and basic reproduction number, number of secondary cases one infected individual can cause in a susceptible population, of leishmaniosis in regards to vertical transmission. The goal of the work presented in this thesis is to address host factors related to the transmission of L. infantum and the way in which co-infections affect the progression of the disease both in the U.S. and in Brazil. Understanding the risk factors associated with the transmission of the parasite Leishmania infantum, the causative agent of the disease, are necessary to controlling and potentially elimination the disease. Utilizing a large prospective cohort and both active and passive surveillance it was identified that leishmaniosis can be maintained in a population via vertical transmission at prevalence rates similar to other endemic countries, 20%. With this knowledge an additional study examining a longitudinal cohort and assessing the impact of tick borne disease co-infections upon disease transmission was performed. It was identified that dogs exposed to three or more tick borne diseases were 11x more likely to progress to clinical disease (Adjusted RR: 11.64 95% CI: 1.22-110.99 p-value: 0.03) than dogs with no tick borne disease exposures. Furthermore, dogs with Leishmania and tick borne disease were 5x more likely to die within the study (RR: 4.85 95% CI: 1.65-14.24 p-value: 0.0051). When examining this relationship in a cross-sectional study in Brazil it was found that dogs with multiple tick borne disease exposures had 1.68x greater risk of being positive for Leishmania (Adjusted RR: 1.68 95% CI: 1.09-2.61 p-value: 0.019). Using a retrospective cohort of dogs and information regarding their dam’s diagnostic status near the time of pregnancy risk factors associated with vertical transmission and the basic reproduction number were calculated. It was found that dogs who were born to dams that were ever diagnostically positive for exposure and/or infection with L. infantum were 13.84x more likely become positive for L. infantum within their lifetime (RR: 13.84 95% CI: 3.54-54.20 p-value < 0.0001). The basic reproduction number for vertically transmitted L. infantum within this cohort was 4.16. The results of these studies suggest that leishmaniosis can be maintained in a population through vertical transmission. Furthermore, the studies show the risk factors associated with vertical transmission relate to the mother’s diagnostic status at time of pregnancy. The results of the co-infection studies highlight the importance of tick prevention in order to reduce disease progression. With increased disease severity associated with increased transmission to potential vectors these studies underline the need for immunotherapies and prevention measures to reduce disease progression in order to reduce transmission. Furthermore, these studies highlight the need for public health control and prevention programs to address vertical transmission if elimination of the disease is to ever be successful.

Thesis (MSc (Veterinary Tropical Diseases)--University of Pretoria, 2009. / Includes bibliographical references. Also available in print format.

Thesis (MSc (Veterinary Science)--University of Pretoria, 2007. / Includes bibliographical references.

Thesis (MSc (Production Animal Studies)--University of Pretoria, 2007. / Includes bibliographical references.

Thesis (Ph. D.) -- University of Texas Southwestern Medical Center at Dallas, 2005. / Vita. Bibliography: 284-323.

The cattle tick, Rhipicephalus (Boophilus) microplus is a tick of veterinary and health importance globally, transmitting Babesia bovis and B. bigemina. Tick control is important and needed to prevent livestock diseases caused by tick-transmitted pathogens. Traditionally, tick control methods have resulted in development of acaricide-resistant ticks, environmental pollution and meat and milk contamination. Therefore, there is a need for alternative method and vaccines directed against tick feeding. The aim of this study was to identify proteins involved in tick feeding, tickhost-pathogen interactions and tick reproduction. Consequently, these will help in identification of antigens with the ultimate goal of developing anti-tick vaccines. R. (B.) microplus female ticks were collected at five different feeding stages. RNA was isolated from the salivary gland extracts (SGEs). The cDNA libraries were synthesized and sequenced with the Illumina MiSeq technology. Transcriptome data was analyzed with CLC Genomics Workbench, Trinity and Minia. The SGEs were also used to isolate the fractions: membrane, soluble and pellet protein for proteomic analysis. The proteomics data was analysed with Mascot, X!Tandem and Scaffold. Both the transcriptome and proteome analysis revealed the presence of major secretory protein families such as Kunitz, lipocalins, serpins, cement proteins and metalloproteases, while the majority of transcripts coded for housekeeping genes. / National Research Foundation (South Africa) / Life and Consumer Science / M. Sc. (Life Science)