High prevalence of drug resistance in animal trypanosomes without a history of drug exposure.
BACKGROUND
Trypanosomosis caused by Trypanosoma congolense is a major constraint to animal health in sub-Saharan Africa. Unfortunately, the treatment of the disease is impaired by the spread of drug resistance. Resistance to diminazene aceturate (DA) in T. congolense is linked to a mutation modifying the functioning of a P2-type purine-transporter responsible for the uptake of the drug. Our objective was to verify if the mutation was linked or not to drug pressure.


RESULTS
Thirty-four T. congolense isolates sampled from tsetse or wildlife were screened for the DA-resistance linked mutation using DpnII-PCR-RFLP. The results showed 1 sensitive, 12 resistant and 21 mixed DpnII-PCR-RFLP profiles. This suggests that the mutation is present on at least one allele of each of the 33 isolates. For twelve of the isolates, a standard screening method in mice was used by (i) microscopic examination, (ii) trypanosome-specific 18S-PCR after 2 months of observation and (iii) weekly trypanosome-specific 18S-PCR for 8 weeks. The results showed that all mice remained microscopically trypanosome-positive after treatment with 5 mg/kg DA. With 10 and 20 mg/kg, 8.3% (n = 72) and 0% (n = 72) of the mice became parasitologically positive after treatment. However, in these latter groups the trypanosome-specific 18S-PCR indicated a higher degree of trypanosome-positivity, i.e., with a unique test, 51.4% (n = 72) and 38.9% (n = 72) and with the weekly tests 79.2% (n = 24) and 66.7% (n = 24) for 10 and 20 mg/kg respectively.


CONCLUSIONS
The widespread presence of the DA-resistance linked mutation in T. congolense isolated from wildlife suggests that this mutation is favourable to parasite survival and/or its dissemination in the host population independent from the presence of drug. After treatment with DA, those T. congolense isolates cause persisting low parasitaemias even after complete elimination of the drug and with little impact on the host's health.
Institute of Tropical Medicine Antwerp, Antwerp, Belgium.
Simbarashe
S
Chitanga
Tanguy
T
Marcotty
Boniface
B
Namangala
Peter
P
Van den Bossche
Jan
J
Van Den Abbeele
Vincent
V
Delespaux
D017954:Africa South of the Sahara; D000483:Alleles; D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016054:DNA, Protozoan / Q000235:genetics; D004133:Diminazene / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D004195:Disease Models, Animal; D004351:Drug Resistance; D051379:Mice; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012641:Selection, Genetic; D014348:Trypanosoma congolense / Q000187:drug effects* / Q000302:isolation & purification*; D014353:Trypanosomiasis, African / Q000188:drug therapy / Q000469:parasitology
D000981:Antiprotozoal Agents; D016054:DNA, Protozoan; C003915:diminazene aceturate; D004133:Diminazene