Infected Camels Research Articles

Serodiagnosis of infection withTrypanosoma evansi in camels in the Sudan

Five diagnostic tests for infection with Trypanosoma evansi have been compared in groups of camels experimentally infected or exposed to natural infection in the Sudan. The correlation of positive results obtained by assays of IgM levels, the mercuric chloride test and the formol gel test with the presence of active infection was unsatisfactory, but there was a good correlation between results obtained using IFAT and ELISA and proven infection. Sera from a high proportion of apparently uninfected camels from endemic areas gave positive reactions with all 5 tests, possibly indicating inadequate parasitological diagnosis or persistence of antibody after unsatisfactory chemotherapy. It was concluded that serological tests using trypanosomal antigens to detect antibodies were more sensitive for diagnosis than indirect tests based on raised euglobulin levels. Serodiagnostic tests may therefore have a place in future programmes for surveillance and control of T. evansi infections in camels.

The prevalence and diagnosis of Trypanosoma evansi infection in camels in southern Ethiopia.

An investigation of trypanosomiasis in camels indicated a high prevalence of infection in southern Ethiopia. Various direct and indirect laboratory methods for the diagnosis of infection with Trypanosoma evansi were compared and evaluated. At the present time inoculation of camel blood into laboratory rodents appears to be the best direct diagnostic method. The formol-gel test and the Takata test appear to be the most sensitive and accurate of the biochemical methods available. However, there still remains a need for an accurate diagnostic test for individual cases.

Observations On the Treatment of Trypanosoma Evansi Infection in Camels

Observations On the Treatment of Trypanosoma Evansi Infection in Camels

The control of camel trypanosomiasis

The control of camel trypanosomiasis (T. evansi type) is most easily effected by diagnosis and cure. In regard to diagnosis, the mercuric chloride test has shown itself to be of high accuracy under laboratory conditions, and although it may lose somewhat in precision under field conditions it is by far the best available method. It has the advantages that it develops in all infected camels, that it develops early in the disease, that it never disappears spontaneously, and that it always disappears following cure. The only faulty diagnoses appear to be due to the existence of a few positively reacting non-infected camels, and to the fact that under field conditions the technique may so suffer from lack of facilities as to permit of apparently positive reactions in healthy camels. Both of these factors have been found in practice to be of little account; healthy camels giving a true positive reaction are extremely rare, and whenever their number is apparently slightly increased owing to the necessity for carrying out tests under bad conditions the only loss is a dose of Naganol. Treatment is universally successful with a single intravenous dose of Naganol. The smallest dose that has been found successful over a long period in the field is 4 grammes, but it is not yet certain that a smaller dose may not suffice. Immunity following cure is for practical purposes non-existent. Camels are certainly resistant to re-infection for a short time after treatment, but the resistance in general practice may be considered as entirely due to residual traces of Naganol, since the resistant period, except possibly in advanced chronic cases, is no greater than that conferred by Naganol alone on healthy camels. For prophylactic treatment Naganol is of some value, but in routine field practice its use in such a manner is not to be recommended, since diagnosis and cure constitute the best control procedure. The period of protection is proportional to the dose administered; with the present routine dose of 4 grammes protection for so short a time as two months is not certain. Circumstances, however, are indicated in which Naganol might profitably be used as a prophylactic. Trypanosome “carriers” among other domestic animals play little part in spreading camel trypanosomiasis. Of the two most closely associated species, the horse in the Sudan is probably never infected, but donkeys may rarely be so, and the infection is of a type that would lead to the establishment of carriers. Suggestions are made for dealing with this situation. In consideration of the foregoing data, it may be simply said that for routine purposes the mercuric chloride test should be freely used, in particular during and at the end of the “fly” season. Any camel showing a positive reaction, either for the first time or at an interval of three months or more after earlier treatment, should be treated. Fortunately for field officers, the seasonal occurrence of camel trypanosomiasis, and the fact that most routine treatments are undertaken towards the end of the “fly” season, ensures that few camels require a second treatment in one year. Regarding the tsetse-borne trypanosomes, camels appear to be susceptible to all species. Infections rarely occur in nature because camels are rarely introduced into tsetse areas. With the exception of Tryp. congolense the infections appear to be comparable with the common one due to trypanosomes of the Tryp. evansi type, and the routine system of control would be applicable. If deliberate exposure of camels to tsetse is ever contemplated an antecedent study of Tryp. congolense infection will be necessary.

Studies In Louping-Ill. (An Encephalomyelitis of Sheep.)

To date, no information is available regarding the infection of camels (Camelus dromedarius) by Anaplasma ovis in North African region. Several animal species can be infected by A. ovis which further complicates its natural infection cycle. In this paper, we investigated the occurrence and the genetic diversity of A. ovis in camels and ticks collected from them in Tunisia and the risk factor analysis. Camel blood samples (n = 412) and tick (n = 300) samples, identified as Hyalomma dromedarii (n = 149, 49.6%), H. impeltatum (n = 142, 47.3%) and H. excavatum (n = 9, 3%), were analyzed by conventional PCR followed by the sequencing of msp4 and groEL genes. A. ovis DNA was identified in five camels (1.2%), but not in infesting ticks (0%). The microscopic examination revealed the specific infection of camel erythrocytes by Anaplasma inclusions. The msp4 and groEL typing confirmed the natural infection of camels by A. ovis and revealed two different msp4 genotypes earlier detected in Tunisian small ruminants and their infested ticks, and five different and novel groEL genetic variants forming a separately sub-cluster within A. ovis cluster. The occurrence of different A. ovis strains specific to camels associated with a low prevalence of this Anaplasma species in camels may enrich knowledge regarding the distribution and the transmission cycle of this bacterium in arid and Saharan areas of Tunisia.

The Mercuric Chloride Test for Camel Trypanosomiasis

Summary 1. A further year's study of the mercuric chloride test has confirmed the view that it is superior in every way to the formol-gel test for the diagnosis of trypanosomiasis in camels. 2. The best technique for use in routine tests in the field is to allow blood to clot, and test the serum the following day by adding one drop to one cubic centimetre of a fairly freshly made 1–25,000 aqueous solution of mercuric chloride. A positive reaction consists in the appearance of opacity within a few minutes. 3. In a total of 242 camels submitted to the test all infected camels have given a positive reaction and all non-infected have given a negative reaction. This constitutes a great improvement on the formol-gel test, in which appreciable numbers of healthy camels give positive reactions and some infected camels fail to do so. 4. Two cases are quoted in which a positive formol-gel reaction was associated with other chronic conditions, but in neither of these was there a positive reaction to the mercuric chloride test. It is, however, difficult to distinguish between conclusions under this section and those under section 3. 5. The difficulty of “partial reactions,” so often observed in the formol-gel test, does not arise. 6. The period elapsing between infection and positive reaction is two or three weeks, as contrasted with the formol-gel test in which it is always longer (possibly averaging six weeks), and in which a positive reaction may never develop. The short “incubation period” is of great importance in detecting the more acute cases. 7. As far as a limited number of retests can be accepted as representative, a positive reaction seems to disappear within about two months of cure (with Naganol). In conclusion, I have to thank Mr. P.A.C. Kenny for carrying out many of the observations during my absences from Khartoum.