The Namangan region in Uzbekistan is an endemic region for human VL as indicated by the high numbers of patients and seropositive children reported from this area during 2006-2008 [4, 5]. Although VL is a reportable disease in Uzbekistan which must be notified to the health authorities, the number of human cases is probably underestimated because of the lack of an efficient reporting system and appropriate diagnostic capabilities. This study has found that a high proportion of dogs are infected in the disease focus. Dogs harbor the same unique L. infantum MON-1 strain group identified in infected children from this region . The fact that L. infantum was the causative agent of canine infection with typical clinical signs, and also of human infection affecting only infants clinically, suggests that a zoonotic form of VL similar in epidemiology to Mediterranean VL is present in Uzbekistan.
The unique L. infantum MON-1 strain group found in the Namangan region differs by MLMT from European, Middle Eastern and North African MON-1 strains. It has been, therefore, suggested that the Uzbeki strains have been circulating in Central Asia for a long time rather than having been introduced recently . This supports the assumption that the Namangan focus is stable and that the disease is likely to have been present in this area for decades.
A significant association was found in this study between the presence of clinical signs compatible with canine leishmaniosis and seropositivity. However, a high proportion of dogs, 20.2%, were seropositive without clinical signs of infection, in agreement with previous surveys on canine leishmaniosis in endemic areas [13, 14]. As found in other studies on canine leishmaniosis, this indicates that dogs in this region are infected asymptomatically and may serve as peri-domestic reservoirs for infection even without showing signs of infection [15, 16]. The presence of clinical signs compatible with leishmaniosis can be helpful for the detection of some of the clinical cases, but it is not sufficient for diagnosis as some cases are infected without clinical signs, and others have non-specific clinical signs such as lymphadenomegaly, splenomegaly and epistaxis that can be caused also by other infectious diseases or inflammatory processes associated with other conditions .
The sensitivity of the PCR technique used in this study was limited due to the fact that it was done on blood in most dogs, which is considered less sensitive than lymph node, bone marrow or spleen [18, 19]. The ITS-1 PCR used is also less sensitive than kDNA PCR, however it is useful for determining the Leishmania species causing the infection . The ability to determine the species of the infecting agent is of particular importance in areas such as the Namangan region where P. sergenti, the major sandfly vector of Leishmania tropica, is present , as this species is able to cause VL in humans and dogs, in addition to being a major cause of human cutaneous leishmaniasis [21–23].
The seroprevalence rate of the dogs studied in the Namangan region is among the highest found in surveys of canine populations in endemic regions, with 8.1% found among dogs in the area of Madrid, Spain, 26% found in Malllorca, Spain, and 29.6% in the south of France [24, 13, 14]. In comparison to studies in other foci of VL, the Namangan region foci is located in an area where there is little awareness among the local population of the fact that this disease is zoonotic and associated with canine infection. No prevention of sand fly bites to dogs using topical insecticides in collars or spot on formulations is practiced as these measures are not available and cost-prohibitive. Vaccines against canine leishmaniosis could potentially also be effective in decreasing canine and human infection , as the Namangan focus is of limited geographic size and a vaccine campaign could reach the majority of households and domestic dogs living in the focus.