High intensity of Tunga penetrans infection causing severe disease among pigs in Busoga, South Eastern Uganda.

BACKGROUND: Towards the improvement of stakeholders' awareness of animal tungiasis, we report 10 unusual severe clinical cases of pig tungiasis which were associated with very high infection intensities of T. penetrans in an endemic area. RESULTS: Morbidity of ten pigs with high sand flea intensities detected during high transmission seasons in an endemic area in Busoga sub region, Uganda is described in detail. The cases of pigs presented with a very high number of embedded sand fleas (median = 276, range = 141-838). Acute manifestations due to severe tungiasis included ulcerations (n = 10), abscess formation (n = 6) and lameness (n = 9). Chronic morphopathological presentations were overgrowth of claws (n = 5), lateral deviation of dew claws (n = 6), detachment (n = 5) or loss of dew claws (n = 1). Treatment of severe cases with a topical insecticidal aerosol containing chlorfenvinphos, dichlorvos and gentian violet resolved acute morbidity and facilitated healing by re-epithelialisation. CONCLUSIONS: The presentations of tungiasis highlighted in this report show that high intensities of embedded T. penetrans can cause a severe clinical disease in pigs. Effective tungiasis preventive measures and early diagnosis for treatment could be crucial to minimize its effects on animal health.

Successful Treatment of Severe Tungiasis in Pigs Using a Topical Aerosol Containing Chlorfenvinphos, Dichlorphos and Gentian Violet.

BACKGROUND: In endemic communities, zoonotic tungiasis, a severe skin disease caused by penetrating female sand fleas, is a public health hazard causing significant human and animal morbidity. No validated drugs are currently available for treatment of animal tungiasis. Due to the reservoir in domestic animals, integrated management of human and animal tungiasis is required to avert its negative effects. METHODS AND PRINCIPAL FINDINGS: A topical aerosol containing chlorfenvinphos 4.8%, dichlorphos 0.75% and gentian violet 0.145% licensed to treat tick infestations, myiasis and wound sepsis in animals in the study area, was tested for its potential tungicidal effects in a randomized controlled field trial against pig tungiasis in rural Uganda. Animals with at least one embedded flea were randomized in a treatment (n = 29) and a control (n = 26) group. One week after treatment, 58.6% of the treated pigs did not show any viable flea lesion whereas all control pigs had at least one viable lesion. After treatment the number of viable lesions (treated median = 0, overall range = 0-18 vs. control median = 11.5, range = 1-180) and the severity score for estimating acute pathology in pig tungiasis (treated median = 1, range = 0-3.5 vs. control median = 7, range = 0-25) were significantly lower in treated than in control pigs (p < 0.001). In the treatment group the median number of viable flea lesions decreased from 8.5 to 0 (p < 0.001). Similarly, the median acute severity score dropped from 6 to 1 (p < 0.001). Every pig in the treatment group showed a decrease in the number of viable fleas and tungiasis-associated acute morbidity while medians for both increased in the control group. CONCLUSIONS: The study demonstrates that a topical treatment based on chlorfenvinphos, dichlorphos and gentian violet is highly effective against pig tungiasis. Due to its simplicity, the new approach can be used for the treatment of individual animals as well as in mass campaigns.

[Serum glucose concentration in subacute intoxication with chlorpyrifos - organophosphate insecticide]. / Stezenie glukozy w surowicy krwi w podostrym zatruciu chlorpyrifosem - insektycydem fosforoorganicznym.

BACKGROUND: Epidemiological studies suggest that exposure to organophosphate insecticides enhances the risk of various diseases, including neurological disorders, e.g. Parkinson's or Alzheimer's disease, arteriosclerosis and diabetes mellitus. For this reason the aim of the presented study was to estimate serum concentration of glucose in subchronic intoxication with low doses of chlorpyrifos, an organophosphate insecticide. MATERIALS AND METHODS: The rats received chlorpyrifos at a daily dose of 0.2, 2 or 5 mg/kg b.w./day for 14 or 28 days. For biochemical determinations of serum glucose in the rats ready-to-use kit was applied. RESULTS: In subacute intoxication with chlorpyrifos the increased serum concentration of glucose was observed after 14 days of intoxication with the highest dose (5 mg/kg b.w.) and after 28 days of intoxication with all dose levels used. CONCLUSIONS: The results of this study showing the increased concentration of serum glucose in subacute intoxication with low doses of chlorpyrifos, as well as the literature data suggest that exposure to organophosphate insecticides can increase the risk of diabetes mellitus. It may thus be concluded that people occupationally exposed to these compounds should be subjected to diagnostic tests for early detection of diabetes.

[Paraoxonase activity and lipid peroxides concentration in serum of rats subchronically intoxicated with chlorpyrifos--organophosphate insecticide]. / Atywnosc paraoksonazy i stezenie nadtlenków lipidów w surowicy krwi szczurów w podostrym zatruciu chlorpyrifosem--insektycydem fosforoorganicznym.

BACKGROUND: Toxicity of organophosphate insecticides is mainly due to the inhibition of acetylcholinesterase (AChE). However, organophosphate insecticides in acute, as well as in chronic and subchronic intoxication may lead to oxidative stress causing the enhancement of lipid peroxidation and changing the activities of antioxidative enzymes. Paraoxonase PON1 is synthesized by the liver. This enzyme hydrolyzes organophosphate compounds, phospholipid hydroperoxides and cholesterol ester hydroperoxides. Its role as an antioxidant has also been suggested. For this reason the aim of the work was to estimate the activity of paraoxonase and the level of serum lipid peroxides in the rats subchronically intoxicated with chlorpyrifos. MATERIALS AND METHODS: The animals received chlorpyrifos at a single daily dose of 0.2, 2 or 5 mg/kg b.w./day for 14 days. For biochemical determinations of paraoxonase activity in serum of rats, Aryloesterase/Paraoksonase Assay Kit (ZeptoMetrix Corporation Buffalo, USA) and for lipid peroxides level, LPO-586 (OXIS International, Foster City, Calif., USA) were used. RESULTS: Chlorpyrifos administration resulted in a decreased activity of paraoxonase in serum. The highest decrease was observed after administration of chlorpyrifos in doses 2 and 5 mg/kg b.w./day. In the intoxication with the highest insecticide dose under study the decreased paraoxonase activity was accompanied by the increased level of lipid peroxides. CONCLUSIONS: In view of the literature data, the finding that low doses of chlorpyrifos lead to statistically significant decrease in paraoxonase activity in serum of rats provides evidence that exposure to organophosphate insecticides induces oxidative stress. It also suggests the need to take into consideration a possible development of arteriosclerosis, hypercholesterolemia and diabetes mellitus in people exposed to these compounds.

[Liver and serum glutathione concentration and liver hydrogen peroxide in rats subchronically intoxicated with chlorfenvinphos--organophosphate insecticide]. / Stezenie glutationu w watrobie i w surowicy krwi oraz nadtlenku wodoru w watrobie szczurów w podostrym zatruciu chlorfenwinfosem--insektycydem fosforoorganicznym.

BACKGROUND: Toxicity of organophosphate insecticides is mainly due to the inhibition of acetylcholinesterase (AChE). However organophosphate insecticides in acute as well as in chronic and subchronic intoxication may lead to oxidative stress causing enhancement of lipid peroxidation and changing the activities of antioxidative enzymes and concentration of non-enzymatic antioxidant. For this reason the aim of the work was to estimate glutathione and hydrogen peroxide levels in the liver, as well as the concentration of total glutathione in serum of rats in subchronic intoxication with chlorfenvinphos. MATERIALS AND METHODS: The animals received chlorfenvinphos, intragastrically with use of a stomach tube, at a one daily dose of 0.3 mg/kg/day for 14 or 28 days. For biochemical determinations BIOXYTECH GSH-400 and BIOXYTECH H2O2-560 Assay kit, OXIS International, Inc., Portland, U.S.A. (reduced glutathione and hydrogen peroxide), and Glutathione Assay Kit, Cayman Chemical Company, U.S.A. (determination of serum total glutathione level) were used. RESULTS: Chlorfenvinphos administration resulted in a decreased level of reduced glutathione in liver accompanied by an increase in liver hydrogen peroxide and serum total glutathione concentrations. The observed changes were more pronounced after 28 days of intoxication. CONCLUSIONS: The common use of organophosphate insecticides results in the environmental pollution, therefore, the decreased liver glutathione level is an additional risk factor for people treated with different medicine (e.g., paracetamol).

Assessment of acetylcholinesterase activity in Clarias gariepinus as a biomarker of organophosphate and carbamate exposure.

The objective of this study was to investigate the response of acetylcholinesterase (AChE) activities in Clarias gariepinus in response to Organophosphates (Ops) and carbamate exposure. The AChE activities were determined in plasma, and eye and brain homogenates of unexposed and exposed fish using Ellman's method and 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) chromophore. The baseline AChE activities in plasma, eyes and brain tissues in unexposed fish were comparable between males and females (P > 0.05). Concentrations of pesticides that inhibited 50% (IC(50)) of AChE activities in brain homogenates following in vitro exposures were 0.003, 0.03, 0.15, 190, 0.2, 0.003 and 0.002 microM for carbaryl, chlorfenvinphos, diazinon, dimethoate, fenitrothion, pirimiphosmethyl and profenofos, respectively. The in vivo dose-effect relationships were assessed using chlorfenvinphos and carbaryl at different concentrations that ranged from 0.0003 to 0.06 microM and 0.0005 to 0.05 microM, respectively. Acetylcholinesterase activities were comparable in plasma, and eye and brain homogenates from control and carbaryl-exposed fish. Following exposure of fish to chlorfenvinphos at concentrations above 0.03 microM, a significant inhibition of AChE activities in plasma (84%) and eye homogenate (50%) was observed. The AChE activities in brain homogenate were comparable between chlorfenvinphos-exposed fish and controls. Because carbaryl cause reversible inhibition of AChE activities was found to be more potent than chlorfenvinphos that cause irreversible inhibition following in vitro exposure. Contrary, carbaryl was less potent than chlorfenvinphos after in vivo exposure possibly due to more rapid biotransformation of carbaryl than chlorfenvinphos. Findings from this study have demonstrated that inhibition of AChE activity in C. gariepinus is a useful biomarker in assessing aquatic environment contaminated by anticholinesterases.

Amphetamine- and scopolamine-induced locomotor activity following treatment with chlorphenvinphos or chlorphyriphos in rats.

OBJECTIVES: Effects of acute exposure to organophosphorous pesticides (OPs), chlorphenvinphos (CVP) or chlorphyriphos (CPF) on amphetamine (AMPH)- or scopolamine (SCOP)-induced open-field locomotion were compared in rats. MATERIALS AND METHODS: CVP and CPF were administered intraperitoneally, both at doses resulting in about 50% inhibition of erythrocyte acetylcholinesterase (rbcAChE). The pesticide groups did not differ one from another in the magnitude of the acute behavioral effects. RESULTS: Three weeks after the exposure, i.e. when AChE activity returned to normal level, the behavioral response to AMPH and SCOP was significantly reduced in CVP-, but not in CPF-pretreated rats. CONCLUSIONS: These results confirm that a single exposure to organophosphorous pesticides may result in neurobehavioral effects detectable after restitution of AChE. They also show that CVP and CPF differ in respect of long lasting functional consequences of exposure, which suggests a difference in the mechanism of toxicity.

Pretreatment with footshock alters some effects of subsequent organophosphate exposure.

Pre-exposure to non-chemical stressors may alter a subject's vulnerability to chemical stressors. We found recently that rats given a subtoxic dose of chlorfenvinphos (CVP), an organophosphorus pesticide, develop behavioral hyposensitivity to amphetamine (AMPH). The present experiments were performed in order to find out whether pre-exposure to a non-chemical stressor several days prior to CVP exposure could influence this effect of the pesticide. In experiment 1 adult male Wistar rats were subjected once to either a short, 5 min (SFS) or long, 20 min (LFS) series of unavoidable footshocks (FS). Twenty-four hours or 14 days after the FS, their open field behavior was tested before and after a test dose of AMPH (0.5 mg/kg. i.p). In experiment 2, the rats were subjected to LFS and 14 days later they were injected intraperitoneally with CVP (1.0 mg/kg) or vehicle (corn oil). In both experiments, serum corticosterone (CORT) levels were determined in separate groups of rats in order to assess the magnitude of the stress response induced by the applied stressors. It was found that: (i) the rise in serum CORT concentration after SFS or LFS was similar in magnitude, while that following LFS was more persistent; (ii) exposure to LFS, but not to SFS, resulted in a decreased response to AMPH on day 14 after the experience; (iii) in rats not pretreated with LFS, CVP exposure resulted in a profound increase in serum CORT concentration. In LFS pretreated rats, however, this effect was significantly reduced; (iv) three weeks after the exposure to CVP, the psychomotor response to AMPH was diminished in control rats but was normal in LFS pretreated animals. The results indicate that pretreatment with a non-chemical stressor may protect the rat against at least some of the effects of an organophosphate pesticide.

The impact of tick control on the productivity of indigenous cattle under ranch conditions in Uganda.

The impact of tick control on the productivity of indigenous cattle was investigated in three herds of East African shorthorn Zebu and Zebu x Ankole (Nganda) breeds, maintained under three tick management systems practised under ranch conditions: twice-a-week dipping, once-a-month dipping, and no tick control. The milk production and the growth rates of pre-weaned and post-weaned calves were monitored once a month over a period of 34 months. Milk offtake was 23% higher during the heavy rainy seasons than in the long dry seasons. Twice-a-week dipping increased the milk offtake by 21% in the second year of study and prolonged the duration of lactation in cows. Similarly, twice-a-week dipping increased the pre-weaning growth rate by 39% in the second year of study, but had no significant effect on the post-weaning growth rate. Generally, the growth rate of calves were greatest during the heavy rainy seasons and least during the long dry seasons. These results provide a basis for assessing the losses under different tick management systems in the various production systems.

Behavioral sensitivity to amphetamine after repeated exposure to an organophosphorous pesticide in the rat. Effect of coexposure to restraint.

In the work environment, chemical stressors coexists frequently with physical or psychological stressors. The purpose of the present experiment was to find out whether the effects of a repeated exposure to chlorphenvinphos (CVP), an organophosphorus pesticide, could be modified by a concurrent exposure to restraint, a psychological stressor. The experiment was performed on male Wistar rats. CVP was administered ten times (one injection/day) at doses of 0.5 or 1.0 mg/kg i.p. (1/30 and 1/10 of LD50, respectively) within a period of two weeks. A half of the rats from each group were immobilized in restraint chambers for 120 min/day starting 10-15 min after CVP injection. In each rat, the effect of 0.5 mg/kg of amphetamine (AMPH) and 0.75 mg/kg of scopolamine (SCOP) on motor activity in an open-field was tested three weeks or six weeks (in rats exposed to 0.5 mg/kg or 1.0 mg/kg doses of CVP, respectively) after the last exposure day. No clear cut effect on the behavioral responsiveness to AMPH or SCOP were noted in rats subjected to repeated restraint, repeated 0.5 mg/kg doses of CVP, or combination of these two stressors. In rats exposed to CVP at the 1.0 mg/kg doses, the behavioral response to AMPH was augmented and this effect was not apparently altered in rats coexposed to restraint. The above result indicates that the repeated exposure to CVP may lead to functional alterations within the central nervous system and that coexposure to restraint neither facilitates nor prevents these alterations from development.

Behavioural responsiveness to amphetamine or scopolamine following repeated exposure to chlorphenvinphos in rats.

A number of reports indicate that exposure to organophosphates (OPs), inhibitors of acetylcholinesterase (AChE), may result in long-lasting neurobehavioural alterations suggestive of an increased cholinergic tone. It is known that rats with cholinergic hyperreactivity are behaviourally hyposensitive to cholinergic antagonists and dopaminergic agonists. The purpose of the present study was to find out whether a similar trait would develop in rats exposed to chlorphenvinphos (CVP), an OP pesticide, in the past. The rats were given ten daily i.p. injections of CVP at doses of 0.5 mg/kg (group P-0.5) or 1.0 mg/kg (group P-1.0). The locomotion stimulating effect of i.p. injection of 1.0 mg/kg amphetamine (AMPH), or 0.7 mg/kg scopolamine (SCOP), was assessed on postexposure day 21 (group P-0.5) or 42 (group P-1.0), i.e. after a time sufficient for AChE recovery. The assessment revealed that in group P-1.0 the behavioural response to AMPH and SCOP was significantly depressed. In rats of the P-0.5 group, however, the behavioural response to each of the drugs was increased. The results suggest that, depending on the exposure level, contrasting alterations in some neurotransmitter systems may be induced by repeated exposure to CVP.

Financial analysis of dipping strategies for indigenous cattle under ranch conditions in Uganda.

A financial analysis was performed to assess the performance of three acaricide-treatment groups of indigenous breeds (Zebu and Nganda) of cattle on a ranch in Luwero District, Uganda. The treatments were based on different frequencies: twice-a-week dipping, once-a-month dipping and no tick control. The objective was to evaluate the economic justification for intensive acaricide application for tick and tick-borne disease control in Uganda. Data were collected by monitoring cattle performance over a period of 34 months. Biological data collected included the number of cows at the beginning and end of the study, net starting liveweight, number of calves born, number of animals dying due to tick-borne diseases and other causes, number of animals sold or slaughtered and milk yield. Records of variable costs (acaricides, drugs, labour, etc.) and output prices were assembled and calculated by treatment group. Gross margin and marginal analysis were used in the financial analysis. The exchange rate in 1990-1993 was one US$ to 1200 Uganda shillings. The gross benefits obtained from animal sales, herd value and milk yield were Uganda shillings 1175, 1389 and 1311 per kg of net starting liveweight for animals dipped twice-a-week, once-a-month and not dipped, respectively. The variable costs were Ug. shs. 424, 390 and 360 per kg of net starting liveweight, respectively. Consequently, the gross margins were Ug. shs. 751, 999 and 951 per kg of net starting liveweight. Furthermore, the marginal rate of return (MRR) in changing from no tick control to once-a-month dipping was 160%, while changing from no tick control to twice-a-week dipping was negative (-313%). The above results showed that the value of increased gains in production obtained from twice-a-week dipping strategy does not offset the costs of inputs for intensive dipping. Once-a-month dipping (strategic) therefore appears to be the most-profitable tick-control strategy for the farmer. The need to conduct further studies in different livestock- production systems and to rationalise future tick control policies is discussed.

Integrated tick and tick-borne disease control trials in crossbred dairy cattle in Malawi.

Crossbred dairy heifers on a farm in an East Coast fever (ECF) endemic area in Malawi were immunised against Theileria parva, Anaplasma spp., Babesia bigemina, Babesia bovis and Cowdria ruminantium. They were treated at infrequent intervals with chlorfenvinphos to limit infestation with adult ticks, without providing complete tick control. In one trial, which tested a threshold dipping regimen, 20 heifers were dipped only once in 6 months to control a flush of Boophilus microplus. Unimmunised controls showed serological evidence of exposure to T. parva and B. bigemina, and one died of ECF, but there were no incidents of tick-borne disease in the immunised group. In a second trial, which tested a strategic dipping regimen, 107 animals were dipped 9 times over a 6 month period. Despite heavy challenge by B. bovis and moderate challenge by B. bigemina and Anaplasma spp. demonstrated serologically, there was only a single clinical case of babesiosis. The observations provide encouragement for the introduction of integrated tick and tick-borne disease control programmes in improved cattle in ECF endemic areas.

Severe post-dipping dermatitis and subcutaneous fluid swellings associated with two outbreaks of sheep scab (Psoroptes ovis infestation)

Large subcutaneous fluid swellings developed on some of the sheep in two flocks infested with Psoroptes ovis during the two weeks after they had been plunge-dipped in phenol-based solutions. The swellings contained between 1 and 10 litres of exudate and affected 4 per cent of the sheep in each flock. The sheep with subcutaneous fluid swellings or exudative dermatitis had significantly lower serum albumin concentrations than the unaffected sheep (P < 0.05). In most cases secondary bacterial infections of the exudate occurred and these necessitated intensive antibiotic therapy. The severity of the skin lesions posed a serious welfare problem.

Effects of a single exposure to chlorphenvinphos, an organophosphate insecticide, on hot-plate behaviour in rats.

Effect of a single i.p. exposure to an organophosphate insecticide, chlorphenvinphos (CVP), in doses of 1.0 and 3.0 mg/kg (one third and one tenth LD50, respectively), on the latency of the paw-lick response (hot plate test) was investigated in rats before and after a short inescapable footshock. The test was repeated twice on the 18th and 19th days after the exposure, i.e. after a time sufficient for a full recovery of cholinesterase activity in the blood and brain. On the first day of testing the groups did not differ with respect to the paw-lick latency before footshock. However, the paw-lick latency after footshock (the index of stress-induced analgesia) was significantly longer in rats exposed to the higher dose of CVP (3.0 mg/kg) than in the control animals. Twenty four hours later, in the control animals, the paw-lick latencies before footshock were shortened in comparison with those recorded on the day before. An opposite effect was observed in the rats exposed to 3.0 mg/kg of CVP. The data suggest that some alterations in the brain functional state may outlast the CVP induced depression of cholinesterase activity.

Neurotoxicity of chlorphenvinphos an organophosphorus pesticide: effects on blood and brain cholinesterase activity, open field behavior and response-to-change in a "T" maze in rats.

Cholinesterase (ChE) activity in blood (plasma and erythrocytes) and in different parts of the brain, open field behavior and response-to-change in a "T" maze were investigated in separate groups of rats after a single intraperitoneal exposure to an organophosphorus pesticide - chlorphenvinphos. The doses used were 3.0 mg/kg or 1.0 mg/kg which amounted to approximately, 1/3 and 1/10 of LD50 for this species. The exposure resulted in a dose dependent inhibition of ChE in blood, as well as in the brain. No marked differences in the level of ChE inhibition in plasma, erythrocytes, and in selected parts of the brain (cerebellum, brain stem, diencephalon, hippocampus and the anterior part of the hemisphere) were noted after a given dose. In general, 3 hours after the exposure, ChE was inhibited by about 80% in the case of the 3.0 mg/kg dose and by no more than 50% in the case of the 1.0 mg/kg dose. In blood as well as in the brain, the normalization of ChE activity proceeded at a similar rate, being accomplished within 14 days and within 94 hours after the 3.0 mg/kg and 1.0 mg/kg dose, respectively. No changes suggesting an impairment of short-term memory were observed in the "T" maze until the end of testing (i.e. up to the fourteenth day after the exposure). In the open field, a short-term decrease (up to the third day) in locomotor and exploratory activity was observed only in rats exposed to 3.0 mg/kg of the pesticide. At the end of testing (10-14th day after the exposure) the introduction of a new object into the open field resulted in an increase of locomotor and exploratory activity in control animals but not in the rats exposed to chlorphenvinphos in the 3.0 mg/kg as well as in the 1.0 mg/kg. This suggests that exposure to chlorphenvinphos may result in some behavioral disturbances lasting longer than the ChE recovery.

Effects of single exposure to chlorphenvinphos, an organophosphate insecticide, on electrical activity (EEG) of the rat brain.

The effect of a single exposure to an agricultural insecticide, chlorphenvinphos (CVP), an organophosphorus anticholinesterase, on neocortical seizure activity induced or promoted by cardiazol, and on hippocampal and neocortical EEG was studied in rats. It was found that CVP, given intraperitoneally in doses of 1.0 and 3.0 mg/kg, resulted in no changes in the number and in the duration of epileptic bursts occurring spontaneously, as well as in the content of the hippocampal theta rhythm. The effect of cardiazol (12.5 mg/kg, i.p.) was slightly diminished when the drug was given 3 hours, but not 14 days, after the injection of CVP. I.p. injection of a carbamate cholinesterase inhibitor, physostigmine, in a dose of 1.0 mg/kg resulted in a dramatic increase of the theta content in the hippocampal EEG, and in the total disappearance of the spontaneous seizures. Determination of cholinesterase activity in blood and in the brain in a separate group of subjects showed that after injection of physostigmine (1.0 mg/kg), the inhibition of this enzyme does not exceed the inhibition after injecting CVP in the doses used. It has been suggested that the differences between CVP and physostigmine in their potential to reduce spontaneous epileptic activity and to induce the hippocampal theta rhythm may be due to somewhat antagonistic action of CVP on cholinergic postsynaptic receptors.