Efficacy of CymelarsatP in the treatmënt of hatural chronic Ttypanosoma evansi infection in camels in the Sudan

Les auteurs ont testé dans les conditions de contrôle en laboratoire, l’efficacité du Cymelarsan” administré par voie intramusculaire (i.m.), dans le traitement des cas chroniques de trypanosomose cameline naturelle à Trypanosoma evansi. Il est confirmé que le Cymelarsan@ administré par voie intramusculaire à des doses de 0,25 ou 0,50 mg/kg de poids vif est un médicament sûr pour le dromadaire. Pendant les 90 jours qui ont suivi le traitement, aucune rechute n’a été observée, avec l’une ou l’autre posologie. Ce médicament est donc pleinement efficace contre les formes chroniques de la maladie naturelle et la dose de 0,25 mg/kg de poids vif en i.m. est recommandée.


Introduction
Cymelarsan@" is a new injectable, trivalent organic arsenical developed for the treatment of animals with trypanosomosis of the Trypanosoma brucei group (5).It has been shown to be very effective against acute T. evansi infection in dromedary camels (6, 8).
The authors have already tested the product against chronic T. evansi infection in camels maintained under field'conditions in the Eastern Sudan (3).Despite the abnormally long and severe dry season experienced during the trial, Cymelarsan@ was found to be very effective.However, a few relapses, or possibly re-infections, occurred from 32 days post-treatment.
The present study is a further investigation of the efficacy of Cymelarsan@ in camels in the Sudan.The main objective was to determine the origin of the trypanosomes detected after treatment in the first'trial, by keeping naturally infected camels under fly-proof conditions after treatment, to exclude any possibility of re-infection.

Source of naturally infected camels
Twenty camels naturally infected with T. evansi were purchased from herds and came1 markets in the vicinity of El-Gedaref (200 km from Kassala), Eastern Sudan.Purchase selection was made on the basis of detection of motile trypanosomes in these animals using the buffy coat examination technique (BCT), and further confirmation as T. evansi by mice inoculation and examination of Giemsa-stained blood smears.Purchased camels were transported by Ion-y to the Regional Veterinary Research Laboratory at Kassala, where this work was conducted.

Pre-treatment examinations and preparations
In the laboratory, 2-3 weeks before treatment, each animal was subjected to routine clinical examinations and regular check-ups for parasitaemia.Jugular vein blood was collected from each animal at weekly inter-vals for assessment of haematological parameters.Serum samples were also collected for fut-ther serological examination.Faecal samples were examined for helminth parasites and Ivomec@ (MSD Agvet) was used for clearance of helminth infestation.All animals were sprayed with Gamatox@ (MallincKrodt Veterinary) to clear tick infestation.
These camels were fed ad libiturq on Sorghum vulgaiis (Durra) and hay.Water was provided every 2 days.Three days before treatment commenced, the camels were individually weighed.Before treatment with Cymelarsan@ the 20 camels were divided into 3 groups as shown in table 1. Retour au menu Retour au menu Four animals in group III were left as infected, untreated controls for 47 days before being treated with quinapyramine'(Trypacide@, Rhône Mérieux) at a dose of 4.0 mg/kg body weight by the subcutaneous (s/c) injection and monitored for 43 days.Therefore, group III is designated untreated controls (group Illa) for the first 47 days, then Trypacide@ treated group (group Illb) for the remainder of the trial.

Post-treatment examinations
During treatment with Cymelarsan@ and Trypacide@, the immediate systemic reactions were recorded on a video tape and the general health condition was authenticated by photography.Immediately after this, the camels were transferred to fly-proof accommodation 90 days.Twelve hours post-treatment with Cymelarsat?, the treated camels were examined for motile trypanosomes by BCT, and examined once every other day for the first week.Thereafter, the camels were examined 2-3 times a week for 11 weeks.Jugular vein blood was collected once every two weeks for haematology.At the end of the experiment, 90 days post-treatment, the camels were released and weighed.

Results
Pre-treatment observations (table Il).
Seventeen of the 20 purchased camels were females of age range 7-12 years.Eight of these females were 5-9 months pregnant.Three were male aged 3-7 years.Eighteen out of the 20 camels were in poor condition.The clinical signs of debility, general weakness, loss of appetite, lacrimation, oedema of the limbs and loss of hair indicated chronic trypanosomosis.
Using the BCT, trypanosomes were detectable in all the camels before treatment commenced.
Parasitaemia was persistent in most of them and f requently disappeared from the others.

Post-treatment observations
Immediate reaction of camels to CymelarsatP and Ttypacide@ Camels treated with Cymelarsan@ tolerated the drug well, showing little reaction at either dose level.Only one camel, which was pneumonie, showed signs of respiratory distress with lateral recumbency and an inability to stand.This effect continued for about 15-20 minutes, after which the came1 returned to normal.There was no adverse effect on pregnant females.The response to Trypacide@ was the classical signs of salivation, urination and restlessness which lasted for a period of more than two hours.

The effect of CymelarsatP on trypanosomes in blood circulation (table I Il)
Examination of blood from all the Cymelarsan@-treated camels after 12 h revealed no detectable circulating trypanosomes.The animals treated with Trypacide@ were investigated after 3 days and one came1 remained positive.This came1 was then re-treated using Cymelarsan@ at a dose rate of 0.5 mg/kg body weight.The trypanosomes then disappeared completely from the circulation until the end of the experiment.The examination of Cymelarsan@treated camels 90 days post-treatment revealed no detectable trypanosomes (table II).Hence, Cymelarsan@ successfully cleared the parasite at both dose levels (0.25 and 0.50 mg/kg body weight).

General body condition and weight
There was a marked improvement in the general body condition which started from the one week after treatment.The most prominent signs of improvement were the disappearance of oedema of the limbs, cessation of lacrimation and growth of new hair.The average body weight increased by 8.03 % in all the camels under Cymelarsan@ treatment.
In animals treated with Trypacide@, it increased by 1 .lO% over a period of one month and a half (table IV).They showed a similar pattern of improvement in condition to that observed in the Cymelarsane group.

Discussion
The results of the present study show that intramuscular administration of Cymelarsan@ produces no local reaction, although an insignificant immediate and transient systemic reaction was observed in a single pneumonie camel.In contrast, subcutaneous administration of the drug (3) produced a hard fibrous swelling felt by palpation of the injection site of treated camels.The present work also show that Cymelarsan@ was capable of clearing trypanosomes from the blood circulation of chronically infected camels within a few hours.This was indicated by the rapid improvement in general health performance observed post-treatment.
It has been well documented that Cymelarsan@ has full activity against the acute form of trypanosomosis due to T. evansi in camels (5, 6, 8).The same finding was observed in this study when chronically infected camels were treated with Cymelarsan@.These results also suggest that in previous work (3) the detection of circulating trypanosomes 32-60 days post-treatment with Cymelarsan@ was due to re-infection.Although the regular provision of water, food, rest and shelter contributed to the complete recovery of the chronically infected camels, the significant increase in body weight (8.03 %) and the good general condition attained in Cymelarsana-treated camels at the end of the trial, cari be attributed to the efficacy of the drug.

Conclusion
Cymelarsan@ is a safe drug for use in camels and is fully effective against the chronic form of came1 trypanosomosis caused by T. evansi when administered by i/m injection at a dose rate of 0.25-0.50mg/kg body weight.A dose of 0.25 mg is recommended.
the haematological values from the pre-and post-treatment period.The camels under tria1 were initially at an advanced stage of anaemia, shown by low PCV values (minimum 18.1 % group III, standard 30-35 %) and RBC counts (minimum 4.01x106/mm3 group II, standard 5.0-l 0.0x1 06/mm3) (2, 7).Over the post-treatment period, some improvement in the PCV values and RBC counts were noted, indicating recovery from anaemia.Pattern of T. evansiparasitaemia in came& before and after treatment, monitored by buffr coat exakzination technique.

*
One of the 8 carnets di ed after the end of the tria/ with twisting neck disease.

TABLE I Trypanosomosis
-infected camels as grouped for the treatment with Cymelarsan @.

TABLE II Group
o No. of positive examinations/Total No. of examinations/(days).

TABLE IV
Average weight gain of T. evansi infected came& 90 days after treatment with Cymelarsan @ and 43 days after treatment with Trypacide @.