Dogmas and misunderstandings in East Coast fever

Assessment of the Impact of Early Diagnosis and Early Treatment in the Integrated Control of East Coast Fever (ECF) Involving Acquired Immunity Induced by Natural Infection in Ankole Cattle

The integrated control of East Coast fever (ECF) by early diagnosis and treatment involving acquired immunity induced by natural infection in Ankole cattle was assessed. A longitudinal study was carried out in Kiruhura district, southwestern Uganda for six months on 244 Ankole breed of cattle from 18 herds under natural tick challenge and relaxed tick control measures. Calves aged three to six months old were recruited and monitored daily by farmers for detection of ECF clinical symptoms. The reported sick animals were treated using Buparvaquone and treatment outcome determined. Monthly follow-ups and blood collections were done to monitor ECF status. Blood was analyzed for Theileria parva parasites by microscopy, DNA by polymerase chain reaction (PCR) and antibodies by enzyme-linked immunosorbent assay (ELISA). The overall prevalence of ECF clinical disease within six months period was 30.3% (74). The major symptoms of early clinical ECF disease were fever and enlarged parotid or prescapular lymph nodes. Clinical cases were categorized as mild, 24% (18) or moderate, 76% (56). There was an overall recovery rate of 100% (74) of the ECF cases whereby 94.6% (70) recovered promptly and 5.4% (4) recovered slowly. Based on blood analysis, prevalence of ECF at baseline was 3.7% (9) by microscopy, 31.1% (76) by PCR and 38.1% (93) by ELISA. A significant increase (p < 0.05) was shown by the increased number of calves with T. parva specific antibodies in the sera from 38.1% at baseline to 68.8% after six months. High antibody levels (positive percentage ≥ 50%) were detected in all ECF-treated and recovered calves at the end of six months. The acquired immunity to ECF was high in treated and recovered cattle, indicating that natural exposure to infection, accurate early diagnosis and effective treatment enhance development of immune-protection in indigenous cattle in an endemic area. The prominent early clinical symptoms for ECF could be exploited in the development of decision support tools for chemotherapy and other integrated control measures.

Safety and Efficacy of the East Coast Fever Muguga Cocktail Vaccine: A Systematic Review

Immunisation of livestock with high quality vaccines is considered an essential approach to controlling many animal diseases. The only currently available commercial vaccine to protect cattle from East Coast fever (ECF), a tick-borne disease caused by Theileria parva, is an unconventional “infection and treatment method” (ITM) involving administration of a combination of live T. parva isolates, referred to as the “Muguga cocktail”, and simultaneous treatment with long-acting oxytetracycline. Veterinary vaccine research and development typically involves studies designed to demonstrate vaccine quality, safety, and efficacy; however, as there were no such purpose-designed registration studies conducted for the Muguga cocktail, evidence for safety and efficacy is solely based on that which is available in the clinical literature. An extensive systematic review was conducted to analyse the evidence available in the literature in order to establish the safety and efficacy of the Muguga cocktail vaccine. A combination of meta-analyses and narrative summaries was conducted. A total of 61 studies met the criteria to be included in the systematic review. The majority of studies demonstrated or reported in favour of the vaccine with regards to safety and efficacy of the Muguga cocktail vaccine. Proximity to buffalo often resulted in reduced vaccine efficacy, and reports of shed and transmission of vaccine components affected the overall interpretation of safety. Better understanding of control options for this devastating livestock disease is important for policymakers and livestock keepers, enabling them to make informed decisions with regards to the health of their animals and their livelihoods.

A cross-sectional survey to establish Theileria parva prevalence and vector control at the wildlife-livestock interface, Northern Tanzania

East Coast fever (ECF) in cattle is caused by the protozoan parasite Theileria parva, transmitted by Rhipicephalus appendiculatus ticks. In cattle ECF is often fatal, causing annual losses >$500 million across its range. The African buffalo (Syncerus caffer) is the natural host for T. parva but the transmission dynamics between wild hosts and livestock are poorly understood. This study aimed to determine the prevalence of T. parva in cattle, in a 30 km zone adjacent to the Serengeti National Park, Tanzania where livestock and buffalo co-exist, and to ascertain how livestock keepers controlled ECF and other vector-borne diseases of cattle. A randomised cross-sectional cattle survey and questionnaire of vector control practices were conducted. Blood samples were collected from 770 cattle from 48 herds and analysed by PCR to establish T. parva prevalence. Half body tick counts were recorded on every animal. Farmers were interviewed (n = 120; including the blood sampled herds) using a standardised questionnaire to obtain data on vector control practices. Local workshops were held to discuss findings and validate results. Overall prevalence of T. parva in cattle was 5.07% (CI: 3.70-7.00%), with significantly higher prevalence in older animals. Although all farmers reported seeing ticks on their cattle, tick counts were very low with 78% cattle having none. Questionnaire analysis indicated significant acaricide use with 79% and 41% of farmers reporting spraying or dipping with cypermethrin-based insecticides, respectively. Some farmers reported very frequent spraying, as often as every four days. However, doses per animal were often insufficient. These data indicate high levels of acaricide use, which may be responsible for the low observed tick burdens and low ECF prevalence. This vector control is farmer-led and aimed at both tick- and tsetse-borne diseases of livestock. The levels of acaricide use raise concerns regarding sustainability; resistance development is a risk, particularly in ticks. Integrating vaccination as part of this community-based disease control may alleviate acaricide dependence, but increased understanding of the Theileria strains circulating in wildlife-livestock interface areas is required to establish the potential benefits of vaccination.

Cattle ticks and tick-borne diseases: a review of Uganda's situation

Herein we review the epidemiology of ticks and tick-borne diseases (TTBDs), their impact on livestock health and on the economy, control and associated challenges in Uganda. Ticks are leading vectors of economically important pathogens and are widespread in Uganda due to suitable climatic conditions. Besides the physical injury inflicted on the animal host, ticks transmit a number of pathogens that can cause morbidity and mortality of livestock if untreated, resulting in economic losses. Uganda suffers an aggregated annual loss (direct and indirect) of over USD 1.1 billion in the TTBDs complex. East Coast fever (ECF) caused by a protozoan haemoparasite, Theileria parva, is the most prevalent and economically important tick-borne disease (TBD) in Uganda and its vector, the brown ear tick (Rhipicephalus appendiculatus) widely distributed. Other prevalent TBDs in Uganda include anaplasmosis, babesiosis and heartwater. We highlight the role of agro-ecological zones (AEZs) and livestock management system in the distribution of TTBDs, citing warm and humid lowlands as being ideal habitats for ticks and endemic for TBDs. Control of TTBDs is a matter of great importance as far as animal health is concerned in Uganda. Indigenous cattle, which make up over 90% of the national herd are known to be more tolerant to TTBDs and most farms rely on endemic stability to TBDs for control. However, exotic cattle breeds are more capital intensive than indigenous breeds, but the increasing adoption of tick-susceptible exotic cattle breeds (especially dairy) in western and central Uganda demands intensive use of acaricides for tick control and prevention of TBDs. Such acaricide pressure has unfortunately led to selection of acaricide-resistant tick populations and the consequent acaricide resistance observed in the field. Vaccination against ECF, selective breeding for tick resistance and integrated tick control approaches that limit tick exposure, could be adopted to interrupt spread of acaricide resistance. We recommend increasing monitoring and surveillance for TTBDs and for emerging acaricide resistance, improved extension services and sensitization of farmers on tick control measures, appropriate acaricide use and the development and implementation of vaccines for the control of TTBDs as more sustainable and effective interventions. A tick control policy should be developed, taking into account variations of agro-ecological zones, farm circumstances and indigenous technical knowledge, and this should be incorporated into the overall animal health program.

Impact of East Coast fever on Grande Comore: assessment taking a participatory epidemiology approach

East Coast fever (ECF), one of the most serious tick-borne diseases in sub-Saharan and eastern Africa, was introduced to the island of Grande Comore in 2002 through zebu import from Tanzania, resulting in at least a 10% loss of livestock. A participatory epidemiology initiative was launched in 2015 to gain a better understanding of ECF epidemiology. Thirty-six villages were investigated involving 36 focus group sessions and 120 individual questionnaires. Farmers' knowledge of ECF and of priority diseases affecting the country was assessed, and the impacts of ECF and other major diseases were compared by a scoring method. The results showed that 69.4% (95% CI [51.3, 87.5%]) of the farmers had good to very good knowledge of ECF. The most important cattle diseases on Grande Comore were considered to be East Coast fever, heartwater, babesiosis, and cutaneous diseases. About 58% of the farmers (95% CI [49.2, 66.8%]) use curative treatments when cattle were sick. Between January and September 2015, the ECF incidence was estimated at 18.5% (95% CI [15.5, 21.4%]), and 87.5% (95% CI [72.7, 100%]) of the cattle infected by ECF died. The ECF incidence estimated in our study was found to be less when compared to that observed in Tanzania even though the climatic conditions in the Union of the Comoros are suitable for the biological vector of ECF, the tick species Rhipicephalus appendiculatus. Access to chemical treatment and its effectiveness against ECF, as well as controlling borders and organizing quarantine, are discussed.

Tick infestations in extensively grazed cattle and efficacy trial of high-cis cypermethrin pour-on preparation for control of ticks in Mvomero district in Tanzania

BACKGROUND

This study aimed at determining the extent of tick infestations in extensively grazed cattle and assess the efficacy of Ecotix® acaricide (2.5% high cis cypermethrin) in Mvomero district in Tanzania. A total of 1200 Tanzanian short horn Zebu (TSHZ) from two farms in two villages were qualitatively assessed for tick infestations and 40 animals (grouped in 10s from each farm) were separated in their herds and quantitatively examined to establish the tick load. The animals were grouped in treatment regime groups (TxRG 1, 2, 3, and 4), TxRG 1 being the control group was treated with water. Ecotix® was applied on day 0 for TxRG 2, days 0 and 7 for TxRG 3 and days 0, 7 and 14 for TxRG 4 and tick load was monitored for 28 days.

RESULTS

All the animals examined were infested with ticks. The identified ticks were Rhipicephalus appendiculatus (55%), Amblyomma variegatum (18%), R. (Boophilus) microplus (12.9%), R. (B) decoloratus (7.1%), R. evertsi evertsi (4.4%) and R. composites (2.6%). The overall mean (mean±SEM) tick density on day zero was 63±30 ticks per animal (ranging from 20-160). The mean tick density on day zero was 44.6±25.4, 74.6±30.3, 55.0±26.2 and 77±33.5 for groups one, two, three and four respectively. Post-treatment quantitative assessment of tick burden revealed that the TxRG 1 animals maintained a tick load throughout the study period. A significant decrease in tick load in animals in groups TxRG 2, 3 and 4 (P=0.0001) with increasing frequency of Ecotix® application was recorded. There was however no significant difference in tick reduction between TxRG 3 and 4 (P=0.0986). Thus TxRG 3 would be sufficient for the monthly tick treatment and with this regime, the farmer would save up to 2.5 USD per animal during six months of dry season.

CONCLUSIONS

The study revealed a high tick infestation among the TSHZ kept in extensive grazing systems in Mvomero district and that when treated with Ecotix® as pour-on preparation using a two application regime per month, the tick control strategy was effective.

Prevalence, associated determinants, and in vivo chemotherapeutic control of hard ticks (Acari: Ixodidae) infesting domestic goats (Capra hircus) of lower Punjab, Pakistan

A total of 800 goats of various breeds, age, and sex were randomly selected from Muzaffargarh (M. garh) and Layyah districts of lower Punjab, Pakistan. The selected goats were visited twice a month to collect information about determinants influencing goat tick infestation prevalence. For acaricidal efficacy, 360 tick-infested adult goats were subjected to an acaricidal treatment and post-treatment quantitative assessment of tick burden. Quantification of adult tick detachment 24 h post-treatment and the duration of treatment efficacy were calculated. Overall prevalence of goat tick infestation in both study districts was 60.1% (481/800). The prevalence was higher in district M. garh than in district Layyah. Tehsil-wise prevalence in district Layyah was highest in tehsil Layyah followed in order by Chaubara and Karor. In district M. garh, highest prevalence was found in tehsil M. garh followed by Kot Addu, Alipur, and Jatoi. Hyalomma a. anatolicum (75.9%; 365/481) and Rhipicephalus sanguineus (24.1%; 116/481) were the predominant species in both the districts. The highest month-wise prevalence was 56.9% and 62.7% in Layyah and M. garh districts, respectively, during July 2008, and the minimum (0%) prevalence was reported in November and December, respectively. Regarding host determinants, female goats were more heavily infested (72.8%) than males (47.5%), and younger animals were (63.5%) more burdened than older ones (56.7%). Teddy goats were the most susceptible breeds followed in order by Beetal, cross-bred, Nachi, and Dera Din Pannah. The preferred sites of attachment were inside and outside of the ear. Both the ivermectin (IVM)- and cypermethrin (CYM)-treated groups resulted in significantly lower (P < 0.05) tick counts relative to controls on all post-treatment counting days. The lowest tick burden in the IVM-treated group was significantly higher (P < 0.05) as compared to the CYM-treated group, the latter being close to zero. Hence, the in vivo efficacy trials of injectable IVM vs CYM pour-on revealed better results for the latter. These observations provided the first insights into what determinants impact goat tick infestation, and laid a foundation for planning of future control programs in the lower Punjab, Pakistan.

In vitro and in vivo efficacies of ivermectin and cypermethrin against the cattle tick Hyalomma anatolicum anatolicum (Acari: Ixodidae)

This study investigated the comparative efficacy of ivermectin and cypermethrin pour-on, for the treatment of Hyalomma anatolicum (a.) anatolicum infestations in bovines. For examining acaricidal efficacy, 480 ticks were exposed in vitro to graded doses of both the acaricides and in vivo efficacy was examined in 360 tick-infested bovines treated at the recommended doses of ivermectin (IVM) and cypermethrin (CYM) pour-on. The comparative quantitative assessment of tick burden was done on days 0, 5, 10, 15, and 20 after treatment using "finger counting." The results of the tick survival assay indicated both compounds were effective in vitro against H. a. anatolicum. The arc transformed mean surviving ticks, 24 h post immersion, was 2.66 and zero in groups treated with the highest dilutions of IVM and CYM, respectively. At 15 days post-treatment, the CYM pour-on showed a higher in vivo efficacy (no surviving ticks) compared to IVM (mean of 20 surviving ticks). A single dose of CYM and IVM was found effective for 20 and 15 days post-treatment, respectively. Additionally, a questionnaire was used to gather information from 30 small holder dairy farms on the farmer's approach toward the control of ticks. The majority (90%) of respondents were using acaricides incorrectly along with poor husbandry practices on their farms. Overuse of IVM in the tested area of Pakistan may be the reason the IVM is not as effective as expected. These results provide useful tools for the decision making in tick control, as well as providing the basis for testing the findings on provincial and national levels in future studies.

A comparison of seroprevalence and risk factors for Theileria parva and T. mutans in smallholder dairy cattle in the Tanga and Iringa regions of Tanzania

A cross sectional serological survey was carried out in two geographical small-scale dairying areas of Tanzania to determine the distribution and prevalence and to quantify risk factors for Theileria parva and T. mutans during the period January to April 1999. The prevalence of serum antibodies to these two Theileria parasites was determined using an indirect enzyme-linked immunosorbent assay (ELISA) technique. The results suggest that the parasites are widely distributed through out the two study sites and seroprevalence of 23% and 48% for T. parva were obtained for Tanga and Iringa regions, respectively. Seroprevalence of T. mutans ranged from 17% in the Tanga region to 40% in the Iringa region. Farm and animal data were collected and analysed by multiple logistic regression models to explore the risk factors associated with seroprevalence to T. parva and T. mutans pathogens. In both regions, seroprevalence for the two Theileria spp. pathogens increased significantly with age. Pasture grazed animals were more likely to be seropositive than those that were zero-grazed. Among individual animal characteristics, seropositivity was higher in cash-bought and charity gifted animals compared to cattle obtained using a formal credit agreement. Further studies on the relative role of risk factors for theileriosis found in this study may assist in the development of an effective control package.

Small-Volume Detection ofPlasmodiumfalciparumCSP Gene Using a 50-μm-Diameter Cavity with Self-Contained Electrochemistry

An electrochemical enzyme-linked immobilized DNA-hybridization assay for the detection of Plasmodium falciparum has been developed. The target molecule was a segment of the repeat sequence of the gene coding for the circumsporozoite (CSP) protein from the AF54087 gene. This analyte offers the possibility of specifically detecting P. falciparum. The assay involves attachment of a biotinylated primary DNA probe via its 5'-amine-terminus to the streptavidin-coated surface of microwells in a 96-well plate. The primary DNA probe (1(0)P, which was of two different sequences we call 1(0)P(a) and 1(0)P(b)) was used to capture the target (T, which was of two different sequences, T1 sequence 481-590 and T2 sequence 472-590 of AF54087 gene for the CSP gene) by hybridization to a complementary sequence on the target. On 1(0)P(a), 47 bases were complementary to T1 and T2 at 543-590, while on 1(0)P(b), 35 bases were complementary to T1 and T2 at 555-590. A secondary DNA probe that contained 36 bases with alkaline phosphatase (2(0)P-AP) label on the 3' end was hybridized to a complementary base sequence on the 5' end of the target. p-Aminophenol, which is enzymatically generated by the immobilized AP from p-aminophenyl phosphate (PAPP), is detected using electrochemistry. The peak current of cyclic voltammograms from a PAPP solution incubated inside the microwells modified with the complete assembly of the assay components gives a linear relationship with the concentration of the target (2-50 ng/mL, where P1 (P1a and P1b) and P2-AP concentrations are 50 ng/mL). A detection limit of 1.4 ng/mL (or 46 pM) of the DNA target was obtained. The signals of the assays were not significantly affected when performed in the presence of human hepatocytes, pig liver, or chicken serum indicating the viability of this assay in real clinical samples.

Strategies, Effectiveness and Rationale of Vector-borne Disease Control in the Pastoralist System of South-western Uganda

In Uganda, control of vector-borne diseases is mainly in form of vector control, and chemotherapy. There have been reports that acaricides are being misused in the pastoralist systems in Uganda. This is because of the belief by scientists that intensive application of acaricide is uneconomical and unsustainable particularly in the indigenous cattle. The objective of this study was to investigate the strategies, rationale and effectiveness of vector-borne disease control by pastoralists. To systematically carry out these investigations, a combination of qualitative and quantitative research methods was used, in both the collection and the analysis of data. Cattle keepers were found to control tick-borne diseases (TBDs) mainly through spraying, in contrast with the control of trypanosomosis for which the main method of control was by chemotherapy. The majority of herders applied acaricides weekly and used an acaricide of lower strength than recommended by the manufacturers. They used very little acaricide wash, and spraying was preferred to dipping. Furthermore, pastoralists either treated sick animals themselves or did nothing at all, rather than using veterinary personnel. Oxytetracycline (OTC) was the drug commonly used in the treatment of TBDs. Nevertheless, although pastoralists may not have been following recommended practices in their control of ticks and tick-borne diseases, they were neither wasteful nor uneconomical and their methods appeared to be effective. Trypanosomosis was not a problem either in Sembabule or Mbarara district. Those who used trypanocides were found to use more drugs than were necessary.

Risk factors for tick attachment to smallholder dairy cattle in Tanzania

A cross-sectional study was conducted in Tanga and Iringa regions of Tanzania, and a longitudinal study in Tanga, to investigate tick-control methods and other factors influencing tick attachment to the cattle of smallholder dairy farms. Most farmers reported applying acaricides at intervals of 1-2 weeks, most used acaricides that require on-farm dilution and most farmers incorrectly diluted the acaricides. Rhipicephalus appendiculatus and Boophilus spp. ticks were those most-frequently encountered on the cattle, but few cattle carried ticks of any species (only 13 and 4.6% of tick counts of the cattle yielded adult R. appendiculatus and Boophilus spp., respectively). Animals were more likely to carry one or more adult Boophilus spp. ticks if they also carried one or more R. appendiculatus adults (OR=14.4, CI=9.2, 22.5). The use of pour-on acaricides was associated with lower odds that animals carried a R. appendiculatus tick (OR=0.29, CI=0.18, 0.49) but higher odds that they carried a Boophilus spp. tick (OR=2.48, CI=1.55, 3.97). Animals >4 months old and those with a recent history of grazing had higher odds of carrying either a R. appendiculatus (ORs=3.41 and 2.58, CIs=2.34, 4.98 and 1.80, 3.71), or a Boophilus spp. tick (ORs=5.70 and 2.18, CIs=2.34, 4.98 and 1.49. 3.25), but zero-grazing management did not prevent ticks attaching to cattle even when combined with high-frequency acaricide treatments. The odds that animals carried ticks varied amongst the agro-ecological zones (AEZs) and administrative districts where the farms were situated-but there was still considerable residual variation in tick infestation at the farm level.

Merogony in in vitro cultures of Theileria parva

In vitro studies were focussed on the duration and cessation of merogony in Theileria parva infected blood lymphocyte cell cultures. The cultures were infected using purified tick stabilates as an alternative to in vitro infections, using sporozoites obtained by labour intensive dissections of salivary glands from infected ticks. After establishment of infection in peripheral blood lymphocytes (PBL), merozoites were temporarily produced for about 2 months after which lymphoblasts only contained schizonts.

An epidemic of East Coast fever on a dairy farm in eastern Tanzania

During the period August-September 1995, an epidemic of East Coast fever occurred at a dairy farm in Morogoro region of eastern Tanzania. Due to an intensive dipping scheme since 1970, a very unstable endemic status had been established in the animals. A breakdown in the dipping scheme caused a major disease outbreak; the dip wash was not changed for 18 months prior to the outbreak and dipping continued in a dip wash of unknown strength. There was also a delay in detecting the disease at an early stage. In total, 180 out of 432 (42%) of the cattle at the farm died--resulting in a loss of Tshs. 26,330,000 (US$ 42,879). The attack risk was nearly 77%. The outbreak points to the importance of adopting integrated strategies for the control of ticks and tick-borne diseases.