Tsetse densities in the intervention and control sites were not significantly different before intervention. The control measures significantly reduced catches of both Glossina palpalis gambiensis and G. tachinoides. The percent FTD reduction in catches of G. p. gambiensis in this study was lower than that reported for the same tsetse species in neighbouring Burkina Faso when deltamethrin pour-on was used . Spray treatments of cattle with 0.05 % deltamethrin have a lower persistency than pour-on treatments with 1 % (0.75 %) of deltamethrin. The number of treated cattle may have been insufficient to achieve a higher reduction of G. p. gambiensis. Another hypothesis may be that a reinvasion of this species from neighbouring untreated areas occured. Catches of both tsetse species were significantly reduced between June 2008 and June 2009 and, FTDs of G. tachinoides reached 0. Although fly catches in the control area remained high, they nevertheless showed a gradual decline. The close proximity of two areas (approximately 35 km apart) could have allowed a spill-over effect with a possibility that cattle in the control area were also treated with insecticides by farmers, hence the decline in the tsetse catch. In the control area, the tsetse catch increased from June 2008 (end of the rainy season) to February 2009 (middle of the dry season) before declining again in June 2009 (start of the rainy season). Riverine tsetse species may disperse away from drainage lines when relative humidity (RH) rises (wet season) and during the dry season retreat to drainage lines, which have a micro-climate able to support their survival .
The reduction in catches of G. tachinoides was higher than that for G. p. gambiensis in both areas. This is consistent with observations from a study which conclusively demonstrated that G. tachinoides almost disappeared from the pastoral zone of Samorogouan (Burkina Faso) following the successful application of deltamethrin pour-on to cattle . It is also easier to control G. tachinoides using insecticide-treated cattle since this fly species prefers cattle as hosts whereas G. p. gambiensis displays an opportunistic feeding behaviour (feeds on a wider range of hosts including monitor lizards) and is hence more difficult to control .
Previous experience has also shown that, unless there is implementation of a forward strategy (i.e. extend the area under control), any area is prone to reinvasion [13, 24]. Otherwise, as in our case of an area about 500 km2 , the objective was limited to tsetse control rather than elimination.
Trypanosome prevalences in both areas were comparable before intervention. There was also a high prevalence of multiple drug-resistant T. congolense in both areas . This changed following tsetse control resulting in an almost 8-fold risk reduction in the area under tsetse control compared to the area without intervention. This reduction is consistent with results from other tsetse control activities [12, 24].
Tsetse control led to a risk reduction of contracting AAT, as expected. The share of infections with T. congolense was lower relative to that with T. vivax, which could also have been mechanically transmitted . It is also acknowledged that young stock is particularly prone to infections with T. vivax as was shown in the Ghibe valley, Ethiopia .
Strongyles were predominant in Sikasso as was the case in other studies in West Africa [27–30]. Egg shedding was seasonal, decreasing during the dry season and then recovering during the rainy season. Egg output suppression occurs during the dry season since some nematode species (Cooperia species, Bunostomum species and Oesophagostomum species) survive as adults while others like Haemonchus species survive as inhibited larvae in the mucosa of the gastro-intestinal tract of their hosts [27, 28].
We observed that egg shedding was dependent on certain animal-specific factors (results not presented here). For instance, cross-bred animals (zebu x trypanotolerant breeds) had comparatively lower FECs than zebu cattle , consistent with findings by Mattioli et al. Additionally, young animals (up to 12 months of age) had higher egg shedding than older ones  indicating a build-up of immunity with increasing age .
It appears that AAT is better tolerated if helminth infections are treated. The risk of AAT in cattle treated with albendazole within the intervention area dropped nearly threefold (2.9 times) compared to the risk in cattle receiving a placebo, although this was not significantly different. A number of reasons could have caused the lack of an outright effect of albendazole treatment on trypanosome infections. Firstly, there was suspected nematode resistance to albendazole, limiting successful nematode control. An anthelmintic drug is considered effective against nematodes if the FECR in anthelmintic treated animals is 95 % and /or the lower bound of the 95 % confidence level must be at least 90 % . In this study, neither of the two thresholds was attained indicating that the treatment was not fully effective in controlling gastro-intestinal nematodes. The causes for this phenomenon are not fully understood. Resistance against albendazole cannot be excluded although, it has not previously been described as a problem in the cotton zone of West Africa. It is also not known which strongyle species were not or insufficiently reacting to the anthelmintic treatment since larval cultures were not performed. Secondly, refugia could have diluted the effect of the albendazole treatments through continued re-infection [33, 34]. Finally, inadequate blinding of the investigators could have made herd keepers aware about the treatments used leading to clandestine treatments with albendazole of cattle belonging to the placebo group.
Consistent with results of trypanosome prevalence surveys during intervention, the data at the end of the intervention indicated a significantly (p < 0.001) reduced trypanosome prevalence in the intervention area from 13.9 % before testing of best-bet strategies to 0.8 % after their implementation. However, a drop in the trypanosome prevalence in the control area was also observed, falling from 17.5 % before the study to 5.8 % at the end. This was attributed to simultaneous reduction of tsetse flies during the study period.
Before intervention multiple drug-resistant T. congolense were dominant in both areas , but no T. congolense were detected at the end of intervention in the area benefiting from tsetse control. This means that the tested integrated best-bet package greatly reduced T. congolense populations thereby contributing to the containment of trypanocidal drug resistance. Dominance of T. congolense had been persisting in the control area at comparable levels before the start of the trial.
Notwithstanding the effectiveness of the integrated best-bet strategies in containing trypanocide resistance, more research is required to demonstrate to what extent reversal of resistance is possible. Further studies to establish the economic viability of such integrated packages are warranted.