Comparative efficacy assessment of pentamidine isethionate and diminazene aceturate in the chemotherapy of Trypanosoma brucei brucei infection in dogs

The chemotherapeutic efficacy of diminazene aceturate (Berenil)--a standard veterinary trypanocide and pentamidine isethionate (PMI)--a human trypanocide was compared in dogs experimentally infected with Trypanosoma brucei brucei. Also, the activities of the drugs on some serum liver enzymes were evaluated before and after treatment to ascertain the relative safety of the drugs. Fifteen local dogs (mongrels) were used for the study. Three of the dogs were uninfected controls, and twelve were infected with a stock of T. brucei brucei. Three of the infected dogs were untreated controls, three were given diminazene aceturate (DA) at 7 mg/kg body weight intramuscularly (i/m), another three received pentamidine isethionate (PMI) at 4 mg/kg i/m on days 14, 17, 19, 27, 29, and 31 post infection (PI) and the remaining three dogs were also given same dose of PMI on days 14, 16, 18, 20, 22, 24 and 26 PI. Both trypanocides effectively cleared the parasites from the blood of the infected treated dogs. However, the infection subsequently relapsed at day 42 PI in one of the dogs in the DA treated group which later died at day 70 PI. Relapse infection was not recorded with the PMI treated groups although two dogs died in the PMI treated group II (treatment at days 14, 17, 19, 27, 29, and 31 PI) without showing relapsed parasitaemia. The packed cell volume (PCV), red blood cell (RBC) count, and haemoglobin (Hb) level which decreased significantly following infection, were reversed by the trypanocidal treatment. The reversal in the red cell values was faster in the PMI treated groups than in the DA treated group. The serum alkaline phosphate (SAP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels increased following infection and drug administration. The increase in the enzyme levels was greater in the DA treated groups than PMI treated groups. It was thus concluded that PMI given at 4 mg/kg i/m at days 14, 16, 18, 20, 22, 24, and 26 PI constituted a safe and efficient trypanocide and exhibited a superior trypanocidal action than DA in T. brucei brucei infected dogs.     

Relapses in dogs experimentally infected with Trypanosoma brucei and treated with diminazene aceturate or isometamidium chloride

Twenty dogs of mixed local East African breeds were used. Five of the dogs were uninfected controls and 15 were infected with T. brucei (ILRAD 273). Five of the infected dogs were untreated controls, five were treated with a high curative dose of diminazene aceturate, (7 mg kg-1 body weight (wt.), and five were given a subcurative dose of isometamidium chloride (1 mg kg-1 body wt.). The drugs, given at 8 days post infection (d.p.i..), led to apparent recovery. The antibody titres, however, remained high in both groups and at 42-49 d.p.i. there was at least one relapse in each treatment group. Parasite populations from relapsed animals were more resistant to the drugs than the original infecting populations. The implications of these findings are discussed.     

Plasma kinetics and efficacy of oral megazol treatment in Trypanosoma brucei brucei-infected sheep

Experimentally infected sheep have been previously developed as an animal model of trypanosomosis. We used this model to test the efficacy of megazol on eleven Trypanosoma brucei brucei-infected sheep. When parasites were found in blood on day 11 post-infection, megazol was orally administered at a single dose of 40 or 80mg/kg. After a transient aparasitaemic period, all animals except two relapsed starting at day 2 post-treatment, which were considerated as cured on day 150 post-treatment and showed no relapse after a follow-up period of 270 days. In order to understand the high failure of megazol treatment to cure animals, a kinetic study was carried out. Plasma concentrations of megazol determined, by reverse-phase high-performance liquid chromatography at 8h post-treatment in these animals, were lowered, suggesting slow megazol absorption, except in cured animals. However, megazol plasma profiles in uninfected sheep after a single oral dose of megazol showed a fast megazol lowered absorption associated with a short plasma half-life of drug. Inter-individual variation of megazol pharmacokinetic properties was also observed. These findings suggested that the high failure rates of megazol treatment were related to poor drug availability after oral administration in sheep. In conclusion, megazol could cure sheep with T. b. brucei infection but oral administration was not an effective route.     

Use of monoclonal antibodies for detecting T brucei brucei infection in splenectomised dogs

A monoclonal antibody against a plasma membrane antigen of Trypanosoma rhodesiense was used for the detection of T brucei group-specific circulating antigen in 24 adult local dogs experimentally infected with T brucei brucei strain 8/18. Ten of the dogs were splenectomised and the remainder non-splenectomised (intact). Five dogs each from the splenectomised and intact groups were inoculated intravenously with try-panosomes. The infected dogs developed trypanosomiasis between days 4 and 8 after infection. The circulating antigens were detected as early as six days after infection and remained high until two weeks after treatment, when the circulating antigen declined. The detection of the antigens showed the existence of infection unlike the antibody test. The treatment of the infected dogs with diminazene aceturate (Berenil; Hoechst) at a dose of 7-0 mg/kg on day 21 after infection cleared all the parasites but elevated the circulating antigen levels. The antigen capture enzyme-linked immunosorbent assay is a useful diagnostic tool for complementing parasitological diagnosis, for detecting infection in the field and for ascertaining the efficacy of trypanocidal drugs.     

Enhanced survival of rats concurrently infected with Trypanosoma brucei and Strongyloides ratti

The interaction between the blood protozoan parasite, Trypanosoma brucei and the gastrointestinal nematode parasite, Strongyloides ratti was studied in outbred white albino rats. Rats were grouped and given either single infection with T. brucei or S. ratti or concurrently infected with both parasites. Blood parasitaemia and packed cell volume, faecal egg/larva output, adult worm burden and survivability were monitored in order to assess the interactive effects of the infections. All trypanosome-infected rats became parasitaemic within 1 week of infection but surprisingly parasitaemia was higher in the single than concurrently infected group of rats. In addition all animals with single T. brucei infection had died by 14 days after the infection, whereas animals with concurrent infection were still alive by day 28 after the infection when the experiment was terminated. Concurrent infection resulted in significant increase in daily S. ratti egg/larval output in faeces (P < 0.01), but lesser number of adult worms were recovered from the intestine of sacrificed rats on day 8 post-infection. Taken together these results suggest that T. brucei and S. ratti interact in a manner that ameliorates their pathogenic effects resulting in a decrease in the level of parasitaemia and intestinal worm burden and in increased life span of the infected rats. These results differ from the classical immunosuppressive attributes of T. brucei and the results are discussed in the context of the possible immune responses that might have contributed to this outcome and the potential significance of the findings in alternative control method of trypanosomosis.     

Prevention and treatment of Encephalitozoon cuniculi infection in rabbits with fenbendazole

The efficacy of fenbendazole for preventing an experimental infection of Encephalitozoon cuniculi and for eliminating the spores from the central nervous system of naturally infected rabbits was investigated. Fenbendazole (20 mg/kg bodyweight daily) was administered from seven days before until two or 21 days after rabbits had been infected orally with 10(6) spores of E. cuniculi. Both regimens were effective in preventing the establishment of the parasites, as demonstrated by negative parasitic-specific serology and by the failure to isolate the parasite from brain tissue. In naturally infected, seropositive rabbits, parasites were successfully isolated from seven of nine untreated animals, but not from the brain tissue of eight animals treated with fenbendazole-medicated pellets for four weeks.     

Efficacy evaluation of epsiprantel (Cestex) against Echinococcus mutilocularis in dogs and cats

Helminth-free dogs and cats were experimentally infected with protoscoleces of Echinococcus multilocularis and used in controlled trials for efficacy evaluation of the cestodicide epsiprantel. In two separate trials each 4 dogs were treated at day 20 post infection (p.i.) with average oral dosages of 5.1 (4.9-5.3) and 5.4 (5.2-5.8) mg/kg body weight (b.w.) epsiprantel, respectively, and necropsied at day 24 p.i. Among each 4 dogs of the two untreated control groups all animals were infected and had high intestinal worm burdens with averages of 33.575 and 100.725 E. multilocularis specimens per animal (individual worm burdens in group Ib 59,500-149,800, group IIb 20,500-43,200); in the two groups of treated dogs the average worm burdens were reduced by 99.6 and 99.9%. Among 8 treated dogs 4 were helminth-free, the other 4 had residual worm burdens (10-70 in 3 dogs, 1480 in 1 dog). In each 5 cats single oral treatments with average doses of 2.7 (2.7-2.8) and 5.5 (5.5-5.5) mg/kg b.w. epsiprantel were 100% effective against E. multilocularis 20 days p.i. and eliminated the worm burdens from all 10 animals. In the untreated group of 5 cats the average worm burden was 2864 per animal (individual worm burdens 20-6830). Side effects of the drug treatment were not observed. The results of the study show that in single therapeutic dosages recommended by the producer (dogs 5.5 mg, cats 2.75 mg/kg b.w.) epsiprantel eliminates E. multilocularis to over 99% or completely, but residual worm burdens may persist in some animals.     

Chemotherapy of T b brucei infection: Use of DFMO, diminazene aceturate, alone and in combination

The therapeutic activity of diminazene aceturate, difluoromethylornithine (DFMO) and a combination of the two agents was investigated in experimental Trypanosoma brucei brucei infections in mongrel dogs. The criteria used in the assessment of the trypanocidal effect of these compounds included the examination of the blood for the parasite, as well as clinical and haematological changes at intervals following treatment. Diminazene aceturate (7 mg/kg intramuscularly), DFMO (300 mg/kg/day orally in three divided doses for six days) and the combination of diminazene aceturate (7 mg/kg intramuscularly) and DFMO (300 mg/kg/day orally for six days) produced an intermittent aparasitemia in the dogs. Relapse infection occurred in all the three groups, but the period of aparasitemia produced by the combination of the agents was longest. The packed cell volume, haemoglobin concentration and red cell count values decreased after the dogs were inoculated with the parasite. The values improved slightly following the treatments with the agents or their combination. The total white blood cell counts in the infected dogs indicated leucocytosis, but this improved with drug treatment.     

Flavonoid mixture ameliorates increase in erythrocyte osmotic fragility and malondialdehyde concentration induced by Trypanosoma brucei brucei-infection in Wistar rats

The experiment was performed with the aim of investigating the effect of a flavonoid mixture, Daflon® 500 mg (DF) on the erythrocyte fragility and lipoperoxidative changes, induced by Trypanosoma brucei brucei infection in Wistar rats. Fifty adult male rats randomly divided into five groups of 10 animals each were used. Rats in the control group were administered (1 mL/kg) distilled water only, while the other groups were infected with T. brucei brucei and treated with Daflon® 500 mg and/or Diminazene aceturate. At the end of 5 weeks, EDTA-blood samples and serum samples were collected from the rats, and were used to determine erythrocyte osmotic fragility (EOF) and serum malondialdehyde (MDA) concentration respectively. The results showed that EOF and MDA concentration significantly (P < 0.05) increased in the infected untreated group when compared to the treatment groups. Treatment with Daflon® 500 mg and Diminazene aceturate significantly (P < 0.05) reduced trypanosome-induced increases in EOF and lipoperoxidative changes, suggesting possible antioxidant properties of Daflon® 500 mg and its therapeutic value in trypanosomosis.     

Recirculation of Trypanosoma brucei brucei in cattle after T. congolense challenge by tsetse flies

The effect of challenging cattle, chronically infected with Trypanosoma brucei brucei, with T. congolense on the development of the T. b. brucei infection was investigated. For this purpose, nine experimental animals were first infected with T. b. brucei through the bites of infected tsetse flies. Once the T. b. brucei had developed into a chronic infection, that was difficult to detect using routine parasitological diagnostic tools, seven of the experimental animals were challenged by tsetse flies infected with T. congolense. Two of the animals infected with T. b. brucei were kept as control. The infection with T. congolense resulted in a sudden increase in the parasitaemia of T. b. brucei. In the T. b. brucei control animals, on the other hand, the parasitaemia remained below the level of detection. The epidemiological repercussions of this increase in the parasitaemia of T. b. brucei after infection with T. congolense are discussed.     

Diminazene aceturate residues in the tissues of healthy, Trypanosoma congolense and Trypanosoma brucei brucei infected dogs

The tissue distribution and residue profile of diminazene aceturate was investigated in healthy dogs and in dogs infected with Trypanosoma congolense and Trypanosoma brucei brucei. The drug was administered at 3.5 mg/kg i.m. and tissue samples were taken post mortem from the animals at 48, 72, 120, 168 and 240 h after injection. The drug was distributed to various organs and tissues of the body with the highest concentrations occurring in liver and kidney. Higher drug levels were obtained in the tissues of healthy dogs compared with trypanosome infected animals except in the brain. The levels of residues in the healthy animals were significantly different (P less than 0.05) from those of the infected dogs. The drug residues were still detectable in the tissues of the animals 10 days after drug administration.     

The response of pigs experimentally infected with Trypanosoma brucei to isometamidium chloride therapy and the relation to nutrition.

Growing pigs were placed on feeds with high (Group A), medium (B) and low (C) dietary energy and were infected with a virulent stock of T. brucei. Eight weeks later, the infected pigs were treated with isometamidium chloride at 1 mg/kg live weight and all pigs were subsequently placed on a high energy diet to investigate their response to therapy. Clearance of T. brucei from blood was completed 72h after treatment. There was no evidence of relapsed infection up to eight weeks after treatment. Red blood cell parameters returned to normal four to six weeks after treatment with responses being fastest in Group A, B and C had gained about two-thirds of the live weight gains of their non-infected pair-fed controls. It appears that the retarded weight gain as a result of the infection persisted after therapy since drug-treated pigs did not gain as much weight as their non-infected controls.     

Suggested dosage rates of melarsoprol in the treatment of mice experimentally infected with Trypanosoma brucei gambiense

One group of BALB/c mice infected with a highly virulent strain of Trypanosoma brucei gambiense were treated intraperitoneally with three series of three injections (each injection of 10 mg/kg) of Mel-B separated by seven days of rest, while a second group was treated once by a single injection All the Mel-B treated mice in both experiments were negative for parasites when examined using either the wet blood film or buffy coat methods, but were intermittently PCR positive during the sampling period. We encourage the use of a repeat negative PCR test over a one month period in combination with corroborative clinical and parasitological investigation to be suggestive of cure in experimental animals previously infected with trypanosomosis. In view of the exorbitant costs of Mel-B and its extreme toxicity, we recommend that Mel-B be given as one course of two injections (each equivalent to 10 mg/kg) separated by 2 d of rest in experimentally infected rodent models.     

Lipopolysaccharide binding protein in the acute phase response of experimental murine Trypanosoma brucei brucei infection

Cellular responses to lipopolysaccharide (LPS) are enhanced by LPS-binding protein (LBP). The present study investigated the acute phase response of LBP during Trypanosoma brucei brucei infection in mice. Mean plasma concentrations of LBP increased two-fold by the seventh day following infection, but decreased to intermediate levels by the 14th day. There were no significant differences in LBP concentrations of infected/antibiotic-treated and infected/untreated mice. At 35 days post-infection, the infected mice were treated with the anti-trypanosomal diminazine aceturate (Berenil^®). LBP levels of the mice then decreased to pre-infection levels within one-week. This demonstrated that LBP is an acute phase protein during murine trypanosomosis. Furthermore, opportunistic secondary bacterial infection during trypanosomosis did not seem to play an important role in the changes in plasma LBP levels. We speculate that the marked concomitant increases in plasma LBP and endotoxin-like activity following murine trypanosome infection might play an important role in the pathogenesis of trypanosomosis.     

The effect of inoculum size and betamethasone treatment on the course of infection with Dictyocaulus filaria in lambs

The effect of Betamethasone treatment on faecal larval production in lambs infected with Dictyocaulus filaria was studied. Four-to-six-month-old male lambs were infected with D. filaria at a dose of 75 larvae per kg body weight (L/kg) and subsequently treated with a total dose of 14 mg of Betamethasone, administered in divided doses, either during the early (day 5–15) or late (day 30–40) stages of infection. Faecal larval yields in treated animals during the period of patency were compared with those of un-treated controls and also with lambs infected with a dose of 150 L/kg.Higher worm establishment, as well as higher percentage survival of infected animals during patency, were associated with infections of 75 L/kg in comparison to 150 L/kg. Treatment with Betamethasone during the early stages of infection resulted in higher worm establishment but similar treatment given during the late stages of infection produced no such effects.The number of larvae per gram of faeces was higher in animals receiving infections of 150 L/kg in comparison to 75 L/kg. Treatment with Betamethasone, whether given during the early or late stages of infection, increased larval output in faeces of infected lambs. However, the output did not reach the levels shown by lambs given infections of 150 L/kg. The total estimated faecal larval yields for the period of patency were higher in the treated animals. The yields were much higher in animals treated during early stages of the infection.     

Flurbiprofen and immunosuppression of Trypanosoma brucei infection in the goat

Goats infected with Trypanosoma brucei and treated with the non-steroidal anti-inflammatory agent flurbiprofen, showed a marked increase in parasitaemia, followed in one of the four goats by death. The in vitro response to mitogens of peripheral blood lymphocytes and separated T- and B-lymphocytes from healthy goats treated with flurbiprofen was normal when compared with non-treated animals. T. brucei-infected goats, not treated with flurbiprofen, showed a marked immunosuppression which was mainly localized in the B-enriched lymphocyte fraction. A combination of T. brucei infection and treatment with flurbiprofen led to even more suppression, because the T-lymphocyte function was also suppressed. It is concluded that flurbiprofen first causes a rise in the parasitaemia and that this high parasitaemia is responsible for the observed immunosuppression.     

Lethal encephalitozoonosis in cyclophosphamide-treated rabbits

Encephalitozoonosis is an opportunistic infection in animals and humans. Its clinical form is observed in immunosuppressed hosts. We studied the occurrence of the manifest form of rabbit microsporidiosis under cyclophosphamide immunomodulation in 40 New Zealand rabbits. The experimental animals were intraperitoneally infected with 5 x 10(7) Encephalitozoon cuniculi spores. Two weeks after infection the animals were treated intraperitoneally with cyclophosphamide, first with 50 mg/kg and then with 15 mg/kg weekly during the 12-week experimental period. Positive controls were either E. cuniculi-infected or cyclophosphamide-immunosuppressed animals. The negative control rabbits remained untreated. Both clinical signs of encephalitozoonosis and depression of peripheral blood cell count developed between weeks 4 and 6 in the experimental animals which died during week 6 of the experiment. No clinical signs compatible with encephalitozoonosis were observed in any of the controls. The results suggest that immunosuppression induced by cyclophosphamide can give rise to a lethal form of encephalitozoonosis.     

Effects of T-2 mycotoxin ingestion on phagocytosis of Aspergillus fumigatus conidia by rabbit alveolar macrophages and on hematologic, serum biochemical, and pathologic changes in rabbits

Rabbits were given T-2 mycotoxin orally at 0, 0.25, 0.5, and 0.75 mg/kg of body weight/day for 21 days. Only rabbits in the 0.75 mg/kg/day group (4 of 5 rabbits) died. Alveolar macrophages were harvested on day 22 and used for in vitro phagocytosis of killed Aspergillus fumigatus conidia. Cultures included sera from untreated rabbits or rabbits treated with T-2. Phagocytosis was significantly (P less than 0.01) reduced in cultures that used serum from rabbits treated with 0.5 mg of T-2/kg/day and alveolar macrophages from untreated rabbits or rabbits treated with T-2. There was little reduction in phagocytosis when alveolar macrophages from rabbits treated with T-2 and normal serum were used. Ingestion of 0.5 mg of T-2 toxin/kg/day significantly (P less than 0.05) reduced weight gain, serum alkaline phosphatase activity, serum sorbitol dehydrogenase activity, and serum bacteriostasis. Similar changes were found in the 0.75 mg/kg/day group, as well as a significant (P less than 0.05) reduction in PCV, total WBC, and differential leukocyte counts. Neutrophil counts decreased, but not significantly (0.05 less than P less than 0.10). Significant changes were not detected in alanine transaminase activity, aspartate transaminase activity, blood urea nitrogen concentration, or complement hemolytic activity. Histopathologic changes consisting of centrilobular hepatocellular swelling, mild portal and periportal fibrosis and lymphocyte necrosis within secondary lymphoid tissues developed in most rabbits treated with T-2. Thymic atrophy, bile duct reduplication, and lymphocyte depletion of secondary lymphoid tissues developed in the group given 0.75 mg/kg/day.(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of moxidectin 1% injectable against natural infection of Sarcoptes scabiei in sheep.

Thirty ewes naturally infected with Sarcoptes scabiei var. ovis, were allocated into three groups of 10 animals each. Animals in groups B and C were treated on day 0 and on days 0 and +10, respectively, with moxidectin 1% injectable at a dose of 0.2mg moxidectin/kg body weight (BW). Group A remained untreated. Seven days before treatment, the geometric mean of Sarcoptes scabiei var. ovis per square centimeter of skin in groups A, B and C were not significantly different. From the day of treatment to the end of the trial, the average number of mites/cm(2) increased in untreated animals and decreased in groups B and C, but these values were higher for group C. Active lesions produced by S. scabiei var. ovis consistently increased during the trial in the untreated animals; in group B the minimum count occurred on day +56 this reduction being more evident in group C (no lesions on days +49 and +56). Also in this group, the number of cured animals was 100%, therefore, the application of two treatments with moxidectin (group C) showed higher efficacy than a single treatment (group B). Body condition score decreased in the three experimental groups along the trial. All animals were individually weighed on days -1, +28 and at the end of the trial. No adverse reactions were observed in the animals treated with 0.2mg moxidectin/kg BW.     

Genetic analysis of virulence factors of Mannheimia (Pasteurella) haemolytica A1

Sixteen 3-week-old calves were intratracheally inoculated with Mycoplasma bovis. Follow-up consisted of regular bronchoalveolar lavages (BALs) and clinical examinations. Animals were slaughtered from 4 to 21 days after inoculation. Counts were made of the mycoplasmas and other bacteria systematically isolated from the BAL liquids and lung lobes after slaughter. On the 6th day, spectinomycin 20mg/kg was given intramuscularly in three repeated doses at 24h intervals to six randomly chosen calves. All animals had developed a persistent M. bovis infection with a maximum BAL count on the 6th day (start of treatment). Co-occuring Pasteurella multocida infection was found in most animals with a maximum rate on the 14th day. The extent of lung surface lesions varied widely (0-64%) but was greater in the later slaughtered calves. Average counts of M. bovis and P. multocida in the BAL liquids were lower in treated calves than in untreated ones but the difference was not statistically significant. However, M. bovis and P. multocida counts in the lungs of the treated group were significantly lower than in the untreated group (p=0.003 and 0.009, respectively).