The Rhipicephalus appendiculatus tick vector of Theileria parva is absent from cape buffalo (Syncerus caffer) populations and associated ecosystems in northern Uganda

Rhipicephalus appendiculatus is the major tick vector of Theileria parva, an apicomplexan protozoan parasite that causes the most economically important and lethal disease of cattle in East and central Africa. The African cape buffalo (Syncerus caffer) is the major wildlife host of T. parva from southern Uganda and Kenya to southern Africa. We show herein that R. appendiculatus appears to be absent from the two largest national parks in northern Uganda. Syncerus caffer is common in both of these national parks, specifically Murchison falls (MFNP) and Kidepo Valley (KVNP). We re-confirmed the previously reported absence of T. parva in buffalo sampled in the two northern parks based on RLB data using a nested PCR based on the T. parva p104 gene. By contrast, T. parva-infected R. appendiculatus ticks and parasite-infected buffalo were present in Lake Mburo (LMNP) in South central Uganda. This suggests that the distribution of R. appendiculatus, which is predicted to include the higher rainfall regions of northern Uganda, may be limited by additional, as yet unknown factors.

Cattle breeding, trypanosomosis prevalence and drug resistance in Northern Togo

African Animal Trypanosomosis (AAT) is a major disease of cattle in Togo and its control is essentially based on chemotherapy. However, because of excessive use of trypanocides during the past decades, chemo-resistance in the parasites has developed. In order to assess the current situation of AAT and resistance to trypanocidal drugs in Northern Togo, a study was conducted on cattle from December 2012 to August 2013 in the regions of Kara and Savanes. An initial cross-sectional survey was carried out in 40 villages using the Haematocrit Centrifugation Technique (HCT). Out of these, 5 villages with a trypanosome prevalence of >10% were selected for a block treatment study (BT) with diminazene diaceturate (DA: 3.5mg/kg for a 14-day follow-up) and isometamidium chloride (ISM: 0.5mg/kg for a 28-day follow-up). Positive blood samples collected during the parasitological surveys and an equivalent number of negatives were further analyzed by PCR-RFLP for trypanosome species confirmation and molecular diagnosis of resistance to DA in Trypanosoma congolense. The results from 1883 bovine blood samples confirmed a high overall trypanosome prevalence of 10.8% in Northern Togo. PCR-RFLP revealed that T. congolense is the dominant pathogenic trypanosome species (50.5%) followed by T. vivax (27.3%), and T. brucei (16.2%). The BT showed varying levels of treatment failures ranging from 0 to 30% and from 0 to 50% for DA and for ISM respectively, suggesting the existence of resistant trypanosome populations in the study area. Our results show that AAT still represents a major obstacle to the development of cattle husbandry in Northern Togo. In areas of high AAT risk, a community-based integrated strategy combining vector control, rational use of trypanocidal drugs and improving the general condition of the animals is recommended to decision makers.

The current challenges of dourine: difficulties in differentiating Trypanosoma equiperdum within the subgenus Trypanozoon

During its 20th annual meeting in Paris in May 1999, the OIE (World organisation for animal health) Ad Hoc Group on Non-Tsetse Transmitted Animal Trypanosomoses expressed the following concerns about dourine: the discrepancies in some of the results of the complement fixation test (CFT), which is the only international diagnostic test officially recognised by the International Organisation for the Transportation of Equidae; the persistence of suspected cases of dourine in some Asian, European and African countries; the impossibility of differentiating Trypanosoma equiperdum from Trypanosoma evansi and of isolating new strains of T. equiperdum from clinical cases that have appeared in various parts of the world since 1982. In the light of these concerns, it was decided, in agreement with the Directorate of the Federal Veterinary Services of Russia in Moscow, to perform comparative trials on the value of CFT/dourine at the OIE Reference Laboratory for dourine in Moscow (The All-Russian Research Institute of Experimental Veterinary Medicine) using reagents (antigens and sera) from seven countries with extensive experience in the field of dourine diagnosis, namely, South Africa, France, Italy, Germany, Russia, the United States of America and the People's Republic of China. It is thanks to the successful co-operation of these countries that the trials were made possible. Results showed an overall concordance and were submitted for consideration to the OIE Biological Standards Commission, the commission which is in charge of the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. These trials serve as a starting point for further study, particularly in the following areas: the isolation of new strains of T. equiperdum from clinical dourine cases; the identification of specific markers for T. equiperdum which would make it possible to differentiate it from among the other species within the subgenus Trypanozoon; the experimental infection of horses with newly isolated T. equiperdum strains to compare their pathogenicity with those currently used in national diagnostic laboratories and with that of T. evansi; phylogenetic studies; the proposal and validation of new, internationally recognised diagnostic test(s) for dourine.

Standardised tests in mice and cattle for the detection of drug resistance in tsetse-transmitted trypanosomes of African domestic cattle

Resistance to the drugs used to control African animal trypanosomosis is increasingly recognised as a constraint to livestock production in sub-Saharan Africa. The most commonly used tests for detection of trypanocidal drug resistance are tests using mice or ruminants, but these suffer from lack of standardisation and hence it may be difficult to compare the results of different investigators. Tests in mice are less expensive than tests in ruminants, but while tests in mice they may be useful as a general guide to resistance in a geographic area they should not be extrapolated to cattle on an individual trypanosome level. Moreover, the commonly used protocols are too laborious for their application to large number of trypanosome isolates on an area-wide basis. This paper presents guidelines for standardised testing of trypanocidal drugs in vivo, and introduces a simplified single-dose test for use in mice, which is convenient for use in areas with limited laboratory facilities. The single-dose test is appropriate for characterisation of geographic areas in terms of trypanocidal drug resistance using large numbers of trypanosome isolates, for making comparisons between areas, and for monitoring changes in trypanocidal drug resistance over time. Multiple-dose tests may be used to determine the degree of resistance of individual stabilates to be determined precisely in mice are also described, but for logistical reasons these will rarely be conducted on more than a few stabilates, and testing of a larger number of stabilates in the single-dose test will generally provide more useful information. Finally, we describe tests in cattle that may be used to determine the efficacy of recommended curative doses of trypanocidal drugs for the treatment of infection with individual trypanosome isolates, including Trypanosoma vivax, which is rarely infective for mice.

Multiple-drug resistant Trypanosoma congolense populations in village cattle of Metekel district, north-west Ethiopia

Investigations were carried out to determine the prophylactic activity of isometamidium chloride in village populations of cattle naturally infected with trypanosomes in Metekel district, northwest Ethiopia. In a cross-sectional study in March 1997, 484 randomly selected cattle from four villages were examined for trypanosome infections by the dark ground/phase contrast buffy coat technique (BCT). The trypanosome prevalence was 17.2%. Trypanosoma congolense was the dominant species accounting for 47.6% of the overall infections. Fifty parasitaemic cattle from two villages were treated with isometainidium chloride (Trypamidium(R)) at a prophylactic dose of 1.0 mg/kg body weight (b.w.) and thereafter monitored on a monthly basis for parasitaemia. Trypanosomes were detected in six cattle within 1 month and in 18 cattle within 2 months of treatment. Twenty three percent (6/26) of cattle infected with T. congolense at the time of treatment were detected parasitaemic with this trypanosome species 1 month after treatment. Mice were infected with three T. congolense isolates obtained from cattle which were detected parasitaemic within one or 2 months after isometamidium treatment. The mice were subsequently treated with ranges of doses of isometamidium chloride or diminazene aceturate (Berenil(R)) and thereafter monitored for parasitaemia for a period of 60 days. Isometamidium chloride at doses of 0.5-4.0 mg/kg b.w. and diminazene aceturate at doses of 3.5-28.0 mg/kg b.w. failed to cure T. congolense infections in any of the animals. Three clones were derived from one of the isolates; each clone expressed high levels of resistance to both trypanocides when tested in mice. Based on these results it is concluded that the prophylactic activity of isometamidium is greatly reduced for some of the T. congolense populations present in the area, and in addition there is resistance to diminazene aceturate in this trypanosome species.

Polymerase chain reaction and DNA probe hybridization to assess the efficacy of diminazene treatment in Trypanosoma brucei-infected cattle

Four of eight Ankole longhorn cattle experimentally infected with Trypanosoma brucei were treated with 7 mg/kg diminazene aceturate (Berenil, Hoechst AG, Germany) at day 71 postinfection. The trypanocidal activity was monitored using polymerase chain reaction (PCR) and DNA probe hybridization. When extracted parasite DNA (without host DNA) was used, as little as 1 fg per reaction, which is equivalent to about 1-10% of the DNA in a single trypanosome, produced a specific product that was visible as a 177-bp band in an agarose gel. In infected cattle, specific PCR products could be amplified at as early as 1 day postinfection. PCR signals remained positive during infection, except in one sample, although aparasitemic phases occurred. In cases where treatment resulted in a significant clinical improvement, PCR signals disappeared at 3-4 days after the administration of the drug. By contrast, in cattle that showed clinical signs of CNS involvement after treatment, although aparasitemic, and died before the termination of the experiment, specific products could be amplified on several occasions following treatment. The PCR signals generated after treatment could be further enhanced by subsequent slot-blot hybridization with a T. brucei-specific DNA probe. We conclude that PCR coupled with DNA probe hybridization provides a highly sensitive tool for the assessment of therapeutic efficiency and disease progression in trypanosome infections, especially in chronic infections when the level of parasitemia is low or when trypanosomes are sequestered at cryptic sites.

A drug incubation Glossina infectivity test (DIGIT) to assess the susceptibility of Trypanosoma congolense bloodstream forms to trypanocidal drugs (Xenodiagnosis)

Blood was collected from two Sahelian goats, experimentally infected with either a drug-sensitive cloned population of Trypanosoma congolense (IL 1180) or a multiple drug-resistant T. congolense stock (Samorogouan/89/CRTA/267) and incubated at 37 degrees C for 30 min and 12 h, respectively, in the presence of different drug concentrations (0.5, 1.0, 10.0 and 100.0 microg/ml blood) of diminazene aceturate or isometamidium chloride. After that, the trypanosome/blood/drug suspensions were offered to tsetse flies (2100 teneral Glossina morsitans submorsitans) through an in vitro feeding system, using a silicone membrane. All tsetse flies were dissected and examined for the presence of trypanosomes in labrum, hypopharynx and midgut 20 days after their infective blood-meals. Infectivity of the drug-sensitive cloned population was already completely abolished after incubation with 0.5 microg/ml of both drugs; however, 13.6-42.2% of tsetse having been fed on untreated blood had developed an infection. In contrast, no significant differences were observed in the infection rates between the experimental groups and their control groups when fed on blood infected with the multiple drug-resistant stock after incubation for 30 min with up to 10 microg/ml of diminazene or isometamidium. In consequence, tsetse appear to be a useful tool in the assessment of drug susceptibility of typanosome populations.

Detection of trypanosome DNA in serologically positive but aparasitaemic horses suspected of dourine in Ethiopia

A field study of horses was conducted in the province of Bale, Ethiopian highlands. A rapid questionnaire analysis indicated that dourine, known as "Dirressa", is a major health problem of equines in this area. A total of 121 horses suspected of dourine were examined by use of clinical, parasitological, serological and DNA based techniques. Incoordination of hindlegs (76%), swelling of external genitalia (48.8%) and emaciation (39.7%) were the most common clinical signs observed. Using the haematocrit centrifugation technique (HCT), no trypanosomes were detected in blood, genital washes or tissue fluids. By contrast, trypanosome specific DNA products were amplified by PCR and subsequently detected by DNA probe hybridization in blood samples of 29 horses (29/104), all serologically positive by CFT and/or ELISA. Positive PCR results were significantly associated with swelling of external genitalia (P< 0.05). There is strong evidence, although there was no direct detection of T. equiperdum, that dourine is highly prevalent in the area, a finding which is in accordance with earlier reports. It is concluded, that this PCR assay provides a very sensitive tool in the diagnosis of active infections of dourine in endemic areas where trypanocidal drug use is common.

Use of a PCR assay for the specific and sensitive detection of Trypanosoma Spp. in naturally infected dairy cattle in peri-urban Kampala, Uganda

The objective of this study was to compare the sensitivity and specificity of the polymerase chain reaction (PCR) with the hematocrit centrifugation technique (HCT) and the mini-anion-exchange centrifugation technique (m-AECT) for diagnosis of trypanosome infections in livestock. In a cross-sectional study, 486 cattle from 50 randomly selected farms in Mukono County, Uganda were investigated in June 1994. The direct parasitological techniques were performed in the field, resulting in 45 (9.3%) animals positive by HCT and 78 (16%) positive by m-AECT. The total prevalence (combined evidence of HCT and m-AECT) was 18.9%, with 78.2% Trypanosoma brucei only, 10.9% T. vivax and 10.9% mixed (T. bruceil T. vivax) infections. Trypanosomes of the subgenus Nannomonas were not detected. DNA was prepared by lysis from 181 randomly selected blood samples and amplified by PCR using species-specific oligonucleotide primers. Overall, the PCR gave positive results in 63 (34.8%) blood samples, with 76.2% positive only for T. brucei, 20.6% positive only for T. vivax and 3.2% positive for mixed (T. bruceil T. vivax) infections. The preliminary results from this study demonstrate that the detection rate of PCR is about two times higher than that of the direct parasitological techniques, suggesting a higher sensitivity. The higher proportion of T. vivax infections detected by PCR as compared to HCT/m-AECT is likely to be due to false parasitological classifications which might occur under field conditions.

Host preferences of tsetse (Diptera: Glossinidae) based on bloodmeal identifications

An enzyme-linked immunosorbent assay (ELISA) was developed to identify the origin of vertebrate blood in the guts of 29 245 wild-caught flies of eleven Glossina species from various ecological zones of Africa. Depending on the quality of the bloodmeal samples, 62.8% of the samples were identified and could be assigned to a host-group (e.g. ruminant), family (e.g. Bovidae) or species (e.g. Bos spp.). A total of 13 145 samples (44.9%) was identifiable up to the species level. With a few exceptions, the present results are in agreement with earlier published reports. Glossina austeni and G. fuscipleuris seemed to have a distinct feeding preference for Suidae (mainly bushpig). Glossina morsitans ssp. fed mainly on Suidae (mainly warthog), although local variations were observed and in some areas hippopotamus or ruminants replaced the warthog as the main host. Bushbuck seemed to be the principal food source for G. longipalpis and G. fusca. Glossina pallidipes fed mainly on ruminants (buffalo, bushbuck and cattle) but, depending on host availability and location, Suidae were also important hosts. Hippopotamus was identified as the main source of bloodmeals for G. brevipalpis. The main hosts for G. longipennis were Suidae (mainly bushpig) and not rhinoceros as had been reported 40 years earlier. The opportunistic feeding behaviour of the palpalis tsetse group was confirmed. The results showed that changes in environment, fauna and host availability may result in modification of tsetse feeding patterns.

Polystyrene as an affinity chromatography matrix for the purification of antibodies

Affinity chromatography is used for the purification of diagnostic polyclonal antibodies in order to ensure specificity. Most commonly, activated bead-formed agarose or its derivatives are used as gel matrices. Alternative matrix materials have been described, but as yet they do not appear to offer important advantages. In this study, pulverized polystyrene (PS 158K, BASF, Mannheim, Germany) was used as a solid phase for the immobilisation of bovine immunoglobulins (Ig). Affinity chromatography was performed using these coated polystyrene beads as the column matrix material in the purification of anti-bovine Ig. The polystyrene binding capacity for the different bovine Ig classes was compared using the Mancini single radial immunodiffusion technique, and ELISA procedures were used to monitor the antibody reactivity of purified and unpurified antibodies. The degree of purification was comparable to the most commonly used procedure using gel matrices from activated bead-formed agarose (e.g. CNBr-activated Sepharose 4B, Pharmacia/LKB Biotechnology, Uppsala, Sweden), but the antibody yield per ml column volume was distinctly lower. In order to raise the yield, such polystyrene bead columns with immobilized antigen can be re-used without loss of activity or larger column volumes can be used to raise the binding capacity. The polystyrene material is quite durable, chemically and immunologically inert and has a long shelf life. We conclude that polystyrene based affinity chromatography is efficient, simple and cheap.

Successful application of deltamethrin pour on to cattle in a campaign against tsetse flies (Glossina spp.) in the pastoral zone of Samorogouan, Burkina Faso

1,500-2,000 head of cattle were treated with deltamethrin 1% Spot On in an area of high tsetse densities, notably of Glossina morsitans submorsitans. After four treatments at monthly intervals, the time between two treatments was increased to two months. 11 months after the commencement of the campaign the fly population had decreased from initially 54.2 flies/trap/day to densities varying between 0.06-2.0 flies/trap/day, mostly G. palpalis gambiensis. Blood-meal analysis showed that this species was surviving in limited areas, mainly feeding on monitor lizards; consequently it is unlikely that this species can be eradicated solely by the use of cattle treated with a pyrethroid. The resistance of Trypanosoma congolense to all commercially available trypanocides necessitated the epidemiological monitoring of calves which were born after the start of the campaign in order to reasses the real challenge. The risk of new infections was low, basically due to contracts between the cattle and tsetse outside the ranching area. A weight increase from 122.3 kg to 213.6 kg of calves aged 6-12 months was recorded from October 1993 to October 1994. An average daily weight gain of more than 400 g was observed from the end of April 1994 to the beginning of August 1994.

Pathogenesis and pathology of African trypanosomosis in Baoulé, N'Dama/Baoulé cross bred and Zebu cattle in Burkina Faso. 1. Clinical performance under high natural tsetse challenge

The pathogenesis and pathology of African animal trypanosomosis (AAT) in Baoulé, N'Dama/Baoulé-cross-bred and Zebu cattle was studied from 1987 to 1991 in a series of experiments conducted under natural and artificial conditions of challenge at the Centre de Recherches sur les Trypanosomoses Animales (CRTA) in Burkina Faso. This first paper reports on the clinical performance of 64 Baoulé, 10 N'Dama/Baoulé-cross-bred and 20 Zebu cattle, which were transferred to the pastoral zone of Satiri, 50 km northeast of Bobo-Dioulasso, a zone infested with Glossina palpalis gambiensis, G. morsitans submorsitans and G. tachinoides. Prior to the experiment, the cattle had been raised in a fly proof stable and at the CRTA breeding station, an area of extremely low incidence of trypanosomosis or had been exposed at least once to natural trypanosome challenge in an area of high Glossina density. The cattle were monitored daily for clinical performance. Blood samples were collected twice weekly and examined on the spot for packed red cell volume (PCV) and parasitaemia. In the blood of 98% of the cattle trypanosomes (Trypanosoma vivax, T. congolense) were detected. Significant inter- and intrabreed differences with respect to the clinical performance were recorded. Regarding general health, the humpless Baoulé and N'Dama/Baoulé cross-bred cattle (Bos taurus) proved to be superior to the humped Zebu cattle (B. indicus) under this high challenge. Previous exposure to natural challenge had a positive effect on survival for both Baoulé and Zebu cattle. The phenotypic variation in response to trypanosomosis was small in Baoulé previously exposed and large in Baoulé previously not exposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of multiple drug resistance of Trypanosoma congolense in Zebu cattle under high natural tsetse fly challenge in the pastoral zone of Samorogouan, Burkina Faso

Preliminary data from an ongoing epidemiological survey in the pastoral zone of Samorogouan (Kénédougou) indicate the occurrence of multiple-drug-resistant Trypanosoma congolense. Despite frequent trypanocidal drug treatments with diminazene aceturate (Berenil, Hoechst) at 7 mg/kg body weight (bw) at intervals of 2 to 4 weeks, no significant drop in the prevalence of African animal trypanosomosis (AAT) was observed. To examine a suspected drug resistance, 20 Zebu cattle, naturally infected with T. congolense and/or T. vivax, were transferred in December 1989 from Samorogouan into a fly-proof stable. Diminazene aceturate at 7 mg/kg bw cured infections of T. vivax, but was ineffective against T. congolense. Likewise, treatments with homidium bromide (Ethidium, FBC) at 1 mg/kg bw and isometamidium chloride (Trypamidium, Rhône Mérieux) at 1 mg/kg bw, respectively, proved to be ineffective. Corresponding chemotherapeutic trials in previously unexposed Zebu bulls and Sahelian goats infected with one primary T. congolense isolate from Samorogouan demonstrated a high level of resistance to diminazene aceturate (7 mg/kg bw in cattle and 17.5 mg/kg bw in goats), isometamidium chloride (1 and 2 mg/kg bw i.v. in goats) and quinapyramine sulphate (Trypacide'S', Rhône Mérieux) at 5 mg/kg bw in goats. The appearance of a multiple-drug-resistant strain of T. congolense emphasizes the urgent need for new chemical substances as trypanocidal drugs and the increasing importance of efficient vector control.