The effects of sub-chronic administration of sub-lethal doses of amitraz/xylene on selected reproductive parameters of male Wistar rats.

This study investigated the effects of sub-chronic administration of sub-lethal doses of amitraz on some testicular parameters of Albino rats. Twenty-four adult male Albino rats (100 ± 10 g) randomly assigned into four groups were used for the study. Groups A, B and C received 10.0, 2.0 and 0.4 mg/kg amitraz in 10 ml/kg water while group D received equivalent volume of water orally and daily for 84 days. Serum testosterone levels (TESL) were assessed on days 0, 28, 56 and 84. Epididymal sperm reserve (ESR), testicular sperm reserve (TSR), testicular weight index (TWI) and testicular histology were evaluated at the end of the experiment. Results revealed dose-dependent reduction (P<0.05) in the mean TESL, ESR and TSR in the amitraz-treated groups as the dose of the amitraz increased. Histological study revealed testicular degeneration characterized by depopulation of seminiferous tubules and depletion of the spermatogenic cells in rats in group A. It was concluded that sub-chronic administration of sub-lethal doses of amitraz could lead to reduced sperm quantity.

The effects of combination of methanolic leaf extract of Azadirachta indica and diminazene diaceturate in the treatment of experimental Trypanosoma brucei brucei infection in rats.

OBJECTIVE: To investigate the effects of combination therapy of methanolic leaf extract of Azadirachta indica (A. indica) and diminazene diaceturate (DDA) in the treatment of experimental Trypanosoma brucei brucei (T. brucei brucei) infection in rats. METHODS: Acute toxicity study of the drug and extract combinations were done. Selection of the best drug and extract combinations was carried out using fifty four rats of both sexes separated into 9 groups. Three dose combinations were derived from selection of the best drug and extract combinations used for the final study viz: 7 mg/kg bw DDA plus 125 mg/kg bw extract (group B), 3.5 mg/kg bw DDA plus 250 mg/kg bw extract (group C), and 1.8 mg/kg bw DDA plus 500 mg/kg bw extract (group D). The final study had in addition to the three groups derived from the dose response study, four other groups viz: uninfected untreated negative control (group F), infected and treated with 3 000 mg/kg bw extract alone (group E), infected and treated with 7 mg/kg bw DDA alone (group A), and infected untreated positive control (group G). The parameters assessed were onset of parasitaemia (OP), level of parasitaemia (LOP), clearance of parasites post treatment (COPPT), relapse infection period (RIP), post infection survival period (PIST). RESULTS: There was no significant difference in OP between the groups (P < 0.05). One day post treatment, the mean LOP of groups A, B, and C were found to be significantly lower than that of group D which in turn was lower than that of group E and G respectively. The mean LOP of group E was significantly lower than group G two days post treatment and this trend continued throughout the experimental period. Mean COPPT of group D was significantly longer than that of groups A, C and B. There was no significant difference in the mean COPPT among groups B, C and A. The mean RIP of group D was significantly shorter than group C, and that of group C was significantly shorter than that of group A. There was no relapse of infection in group B. The PIST of group E did not differ significantly from group G. CONCLUSIONS: This experiment stands to conclude that combination of 125 mg/kg bw extract and 7 mg/kg bw DDA is very effective in the treatment of trypanosomosis, caused by T. brucei. This combination therapy proved to be better than single therapy of DDA.

Trypanocidal resistance in Trypanosoma evansi in vitro: effects of verapamil, cyproheptidine, desipramine and chlorpromazine alone and in combination with trypanocides.

A study was conducted in vitro to assess the ability of calcium antagonists to reverse trypanocidal resistance in Trypanosoma evansi. Susceptibility patterns of sensitive and resistant parasites were evaluated against calcium antagonists of several chemical classes (verapamil, cyproheptidine, desipramine and chlopromazine), alone and in combination with suramin, diminazene aceturate or melarsen oxide cyteamine. The putative resistance modulators were intrinsically antitrypanosomal, but were unable to reverse resistance to any of the trypanocides tested. It was thus concluded that resistance to these trypanocides in T. evansi may differ from drug resistance mechanisms occurring in cancer cells, malaria or in South American trypanosomosis, where calcium antagonists have successfully reversed resistance.

The effects of hyperosmolar agents lithium chloride and sucrose on the brain concentration of diminazene aceturate in rats.

The concentrations of diminazene aceturate in the brain of Trypanosoma brucei brucei infected and uninfected rats treated with diminazene aceturate (3.1 mg/kg, im) and either LiCl (2.5, 5.0 and 10 micrograms/kg) or sucrose (0.25, 0.5 and 1.0 g/kg) were determined. When diminazene aceturate was administered at a standard dose of 3.1 mg/kg (im), the addition of LiCl (10 micrograms/kg, im) increased significantly (P < 0.05) the concentration of the drug in the brains of both trypanosome infected and normal infected rats. The addition of sucrose (1.0 g/kg, im) instead of LiCl failed to give any significant increase in diminazene aceturate levels in the brain. The diminazene aceturate levels were significantly (P < 0.05) higher in the organs (brain, kidney, liver and spleen) of trypanosome infected compared to uninfected rats. The concentration of diminazene aceturate in the organs increased significantly (P < 0.05) with increasing concentrations of LiCl.

The chemotherapeutic efficacy of diminazene aceturate and lithium chloride against relapse infection of Trypanosoma brucei brucei in rats.

The chemotherapeutic efficacy of diminazene aceturate (Berenil) and lithium chloride (LiCl) in relapse infection of trypanosomiasis was investigated in rats experimentally infected with Trypanosoma brucei brucei. The study showed that the combination of diminazene aceturate at (7 mg/kg) and LiCl (10 micrograms/kg) appeared more effective therapeutically than diminazene aceturate, or diminazene aceturate and LiCl and dexamethasone group, as more of the rats in the diminazene aceturate and LiCl treated-group remained aparasitaemic for longer days (60 days). Relapse parasitaemia occurred on days 10 and 12 in diminazene aceturate (7 mg/kg); diminazene aceturate (7 mg/kg) and LiCl (10 micrograms/kg) plus dexamethasone (1 mg/kg) treated group respectively, while relapse parasitaemia did not occur in the diminazene aceturate and LiCl treated group until day 20. Histopathological examination of the brain did not show any signs of inflammatory reaction in the diminazene aceturate and LiCl and dexamethasone treated group. However lesions associated with meningoencephalitis, such as cellular infiltration of mononuclear cells, perivascular cuffings and perivascular congestion and oedema were observed in the diminazene aceturate; diminazene aceturate and LiCl treated groups.

Treatment of experimental trypanosomiasis in pigs.

The therapeutic activity of difluoromethylornithine (DFMO), diminazene aceturate (Berenil) and their combination against chronic trypanosomiasis was investigated in experimental Trypanosoma brucei brucei infections of growing pigs. DFMO (300 mg/kg/day orally for 10 days), diminazene aceturate (7 mg/kg in single intramuscular injection) and a combination of the two agents at the above dosages produced varied periods of aparasitaemia in the treated pigs. Relapse parasitaemia occurred in all treatment groups, with diminazene aceturate providing the longest relief period of 17 days, combination treatment 11 days and DFMO 6 days. The packed cell volume, blood haemoglobin concentration and red cell count values decreased after the pigs were infected with the parasites. The values improved following treatment with the agents and their combination.

Comparative study of clinical signs, haematology and prevalence of trypanosomiasis in Holstein Friesian and White Fulani Zebu cattle exposed to natural infection in a rain forest zone of Nigeria.

A comparison of the symptomatology, haematology and prevalence of trypanosomiasis in Holstein Friesian and White Zebu cattle exposed to natural infections on a ranch in a rain forest zone of Nigeria is presented. 23 (44%) of the adult Friesians had trypanosome infections with a generally heavy parasitaemia. Infection was light in the Friesian calves and the Zebus with infection rates of 2 (6.9%) and 3 (15%) respectively. Trypanosoma vivax was the sole species encountered on the farm. There was a general unthrifty appearance in the adult Friesian herd as well as classical signs of trypanosomiasis. The Friesian calves and Zebus were generally in good conditions with an appearance of good health except one each of the infected animals which showed apparent symptoms of the disease. There was a marked reduction of the red cell values of the infected adult Friesian and Zebu cattle. The red cell values of the uninfected adult Friesians were equally depressed suggesting cryptic infections or that they were cured parasitologically by the recently administered trypanocide. The Friesian calves had normal red cell values for both the infected and uninfected. Leucocyte counts were generally high on the Farm and higher for the infected animals.

The production performance of imported Friesian cattle under heavy Trypanosoma challenge in a rain forest zone of Nigeria.

The productivity of 76 newly imported pregnant Friesian cattle and two bulls under heavy trypanosome challenge in the rain forest belt of Nigeria is reported. At the first visit in August 1989 and within 7 months of arrival of the heifers, the herd population had reduced by 26 (33.3%) as a result of deaths (six animals) and culls/salvages (20). The surviving 52 animals were generally in poor health with classical symptoms of trypanosomiasis. Thirty-one (40.8%) of the pregnancies were unsuccessful because of abortions (13 animals), premature births (seven), embryonic deaths (five) and death of heifers (six). Of the 45 successful calvings, 16 perinatal deaths occurred. All serum samples were negative for brucellosis. Only 41 (63.1%) of the 65 productive heifers lactated of which 24 (58.5%) yielded milk only for 6 months and less. The remaining 17 (41.5%) heifers were still at different stages of lactation ranging from 3 to 7 months within the period of analysis. Treatment with isometamidium (Samorin) at 0.5 mg/kg body weight cured the infection and prevented reinfections and/or relapses within 3 months of administration. A rise in the haematocrit and milk production after Samorin treatment was recorded. Careful analysis of the outbreak indicated that the reproductive wastages and poor lactational performance may have been induced by the severe trypanosomiasis diagnosed in the herd.

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.

Effects of chronic oral administration in mice of the gut-stimulating crystals of Croton penduliflorus seed oil.

Crystals from Croton penduliflorus seeds (CPC) were administered at weekly intervals in two doses (7 mg/kg and 21 mg/kg) by gastric intubation to mice over 12 weeks. CPC induced purgation in the treated mice, with the higher dose having a more profound effect. Mice treated with CPC developed skin lesions with swollen scrotums. There were significant changes in the PCV, Hb and plasma proteins of treated mice. Gangrene of the tail with subsequent sloughing was observed, particularly in the low dose group. Mice in the low dose group also experienced retarded growth. A significant clinical finding in the treated mice was abortion during late pregnancy and 100% fetal mortality. It was concluded that, apart from its purgative effect, CPC can cause toxic effects in chronic administration. Use in pregnant women should be discouraged.

Effects of the combination of DL-alpha-difluoromethylornithine and diminazene aceturate in Trypanosoma congolense infection of dogs.

The therapeutic activity of a combination of difluoromethylornithine (DFMO) with diminazene aceturate was investigated in mongrel dogs experimentally infected with Trypanosoma congolense. The criteria used in the assessment of the trypanocidal effect of the therapy include the examination of the blood for parasites, as well as clinical and haematological changes at intervals following treatment. Diminazene aceturate and DFMO alone and in combination produced intermittent aparasitaemia in the dogs. Although relapse infection occurred with all three treatment regimes, the drug combination gave the best result. The packed red cell volume, haemoglobin concentrations and red blood cell values decreased significantly following parasite inoculation but increased after treatment. The total leucocyte counts decreased in all the infected dogs but improved with treatment, and the differential leucocyte counts indicated neutropenia in all the infected animals prior to treatment.

Effects of trypanosomal infection on the pharmacokinetics of diminazene aceturate in dogs.

Pharmacokinetics of diminazene aceturate (3.5 mg/kg) was investigated in normal mongrel dogs and in those infected with Trypanosoma brucei brucei. After intravenous injection the decrease in concentration followed a biphasic process with mean elimination half-life (t1/2 beta) of 9.87 hr in healthy dogs and 12.51 hr in T. b. brucei infected dogs. The mean total body clearance (cl) of diminazene aceturate in healthy dogs (0.62 l/kg/hr) was significantly lower (p less than 0.05) when compared to that of the infected animals (0.47 l/kg/hr). The distribution half-life (t1/2 alpha) was significantly (p less than 0.05) decreased in dogs after infection (0.14 hr) compared to 0.2 hr observed in the same animals before infection. The mean diminazene recovered in the urine of normal dogs (28.18%) was not significantly different from that recovered from infected dogs (26.1%). These results indicate that infection with T. b. brucei markedly retards the total body clearance of diminazene and also hastens the distribution of the drug when administered intravenously.

Effects of the gut-stimulating principle in Croton penduliflorus seed oil on the central nervous system.

The gut-stimulating principle in Croton penduliflorus seed oil isolated as white crystals (CP crystals) significantly reduced pentobarbitone-induced sleeping time in mice at doses of 3 and 6 mg/kg intraperitoneally. Indomethacin (4 mg/kg) and atropine (0.044 mg/kg) significantly reversed the action of CP crystals on pentobarbitone sleeping time with indomethacin having a profound reversal effect. CP crystals significantly reduced the mean onset of convulsions and the mean death time in mice treated with a surely convulsive dose of strychnine. CP crystals significantly reduced the intensity of morphine and pethidine analgesia and prolonged the duration of pethidine analgesia. Most actions of CP crystals suggest that it stimulates the CNS and reduces the intensity of opioids (except codeine) while prolonging their duration of analgesic action.

The toxic effects of a chronic administration of the gut-stimulating principle in Croton penduliflorus hutch. seeds in mice.

Albino mice (8-10 wks) weighing between 14 and 25 g were divided into 2 groups and dosed orally once per week with 2 doses (7 mg/kg and 21 mg/kg) of the gut-stimulating principle in Croton penduliflorus seeds (CP crystals) for 12 weeks. Some mice (3-4) from each group were killed at 10 days intervals for the first 6 wks of the experiment and at 20 days intervals for the last 6 weeks. Gross and histopathological changes in the brain, heart, liver, kidney, adrenal, spleen, testis, lung and various segments of the gastrointestinal tract including the stomach, duodenum, ileum and colon were observed. The relative weights of the visceral organs were also recorded. Significant weight change in the spleen was evident. The congestion of the lung was the most common gross pathological observation made. Other observations were splenomegaly, enlarged heart, swollen uterine horns, etc. Histopathological changes observed included haemorrhages in the lungs, myocardium, liver, kidney, testis, brain etc. Goblet cell hyperplasia with mucin present in the lumen were observed in the jejunum, ileum and colon. In conclusion, CP crystals produced severe lesions in the visceral organs and the brain after chronic oral administration at low and high dosage levels which should indicate caution in administering the extract to humans.

The influence of Trypanosoma congolense infection on the disposition kinetics of diminazene aceturate in the dog.

Diminazene aceturate was administered intravenously at 3.5 mg/kg body weight to mongrel dogs before and after infection with Trypanosoma congolense. Plasma and urine were collected at varying intervals thereafter and analysed for the compound. The mean area under the concentration-time curve (AUC) of diminazene in healthy dogs was 25.8 h.micrograms/ml but was significantly increased (p less than 0.05) to 35.7 h.micrograms/ml after infection with T. congolense. The distribution half-life was significantly reduced (p less than 0.05) in dogs after infection, being 0.12 h compared to 0.17 h in the same dogs before infection. The mean proportion of the diminazene recovered in the urine of infected dogs (25.1%) was not significantly different from that recovered in the urine of healthy dogs (26.8%). These results indicate that infection with T. congolense increases the rate at which diminazene is distributed in the body but that the infection has no marked influence on the urinary excretion of the drug.

Chemotherapy and pharmacokinetics of some antimicrobial agents in healthy dwarf goats and those infected with Ehrlichia phagocytophila (tick-borne fever).

The therapeutic efficacy and pharmacokinetics of oxytetracycline (10 mg kg-1), ampicillin (20 mg kg-1) and a combination (TSS) of trimethoprim (20 mg kg-1), sulphadimidine (50 mg kg-1) and sulphamethylphenazole (50 mg kg-1) were investigated in normal dwarf goats and in those infected with Ehrlichia phagocytophila. Goats given oxytetracycline or TSS intravenously showed improvement, whereas ampicillin was ineffective. The infected goats had significantly prolonged elimination half-life values for sulphadimidine and oxytetracycline. The disposition kinetics of ampicillin and sulphamethylphenazole showed no marked differences between the healthy and infected animals. The tick-borne fever model used in the present study can be of value in testing the therapeutic efficacy and pharmacokinetics of chemotherapeutic agents in rickettsial infections.

Anorexia during febrile conditions in dwarf goats. The effect of diazepam, flurbiprofen and naloxone.

The most common sign of febrile diseases is anorexia, which develops at a time when adequate caloric and micronutrient availability may be critical. In order to study the relationship of fever and anorexia, feed intake in dwarf goats was studied under conditions of fever and antipyresis. Furthermore, experiments were done to establish whether a feed intake stimulant would override the anorexia during febrile conditions. Infection with Ehrlichia phagocytophila and i.v. injection of Escherichia coli endotoxin (0(111) B4, 0.1 microgram/kg body weight) both resulted in increased rectal temperatures and significant reductions in feed intake. Administration of the antipyretic drug flurbiprofen (1 mg/kg) to febrile animals inhibited the temperature responses, but food intake was still suppressed. Diazepam (0.06 mg/kg), a feed intake stimulant, did not override the anorexia associated with fever. Blocking the febrile response of E. coli LPS-injected goats with flurbiprofen plus diazepam or with flurbiprofen plus naloxone (0.1 mg/kg) did not antagonise their reduced feed intake either. The effects of these drugs and of endotoxin on rumen motility adds an interesting aspect to their activities in the CNS, since the CNS has been shown to regulate various aspects of forestomach motility, which in turn could alter feeding behaviour. Moreover, our findings are consistent with the hypothesis that the suppression of feed intake might depend on the release of interleukin-1.

Effect of tick-borne fever on the disposition of sulphadimidine and its metabolites in plasma of goats.

The effect of tick-borne fever (TBF) on the plasma disposition of sulphadimidine (SDM) and its metabolites in goats was studied. In uninfected goats, SDM was extensively metabolised mainly by hydroxylation, glucuronidation and to a minor extent by acetylation. In TBF infected goats the hydroxylation of SDM into 6-methylhydroxysulphadimidine (SCH2OH) as well as into 5-hydroxysulphadimidine (SOH) was markedly reduced (-57.6 and -63.6 per cent, respectively). An unidentified metabolite (metabolite X) was detected, which was largely glucuronidated in the uninfected goats. In the TBF infected goats the glucuronide derivatives of the X metabolite and of SOH were barely detectable. In TBF infected goats the plasma concentration of the N4-acetylated metabolite (N4-SDM) was decreased to a lesser extent (-22.1 per cent) than the hydroxy metabolites. Due to the diminished metabolism the elimination half-life of SDM was increased 1.8 times and the total sulphonamide body clearance was diminished compared with findings in the control experiments.

Diazepam and chlorpromazine stimulate feeding in dwarf goats.

5 adult dwarf goats were injected intravenously with diazepam, chlorpromazine or isotonic saline. Both diazepam at 0.04 mg/kg and chlorpromazine at 0.5 mg/kg significantly stimulated food intake above the control 0.9% NaCl levels. The stimulatory effect appears to be most pronounced within the first 15 min post injection, and was no longer evident between 30 and 45 min after the bolus injection of the tranquillizers.