ROME/ITALY, July 26th (Biermann) – A research team from Istituto Superiore di Sanità, led by Dr. Marina Gramiccia, evaluated detection of canine Leishmania infections by conjunctival swab analysis. Furthermore, they aimed to find a correlation with entomological parameters

The longitudinal study was carried out on kennelled stray dogs in a canine leishmaniasis (CanL) endemic area. Gramiccia and colleagues examined the early and late diagnostic performance of a non-invasive conjunctival swab (CS) nested (n)-PCR analysis for Leishmania detection in 2 cohorts of dogs, respectively.

Cohort A consisted of  65 IFAT- and CS n-PCR-negative dogs exposed to a full sand fly season (July–November 2008). In parallel, a sand fly survey was performed on site using standard sticky traps set twice a month, for a cumulative surface of 63 m2.

Cohort B comprised 17 IFAT- and CS n-PCR-negative dogs found positive in July 2008 at the peripheral blood buffy-coat (BC) n-PCR. These dogs were examined again by BC n-PCR in September and November 2008, and before the subsequent transmission season (May 2009) along with CS n-PCR and IFAT.

None of the cohort A dogs converted to positive CS n-PCR during the transmission season. Although 2500 phlebotomine specimens were collected with peaks of 100–147 specimens/m2 sticky trap, the cumulative density of the only proven CanL vector in the area (Phlebotomus perniciosus) was found to be very low (0.5/m2).

All dogs in cohort B remained substantially seronegative; BC n-PCR showed an intermittent positive trend during the period surveyed, resulting in 82% conversions to negative by the end of the study, in contrast with 71% conversions to positive at the CS n-PCR analysis.

The investigators conclude that while CS n-PCR was not found effective for the early detection of Leishmania contacts in dogs exposed to a low pressure of vectorial transmission, this assay showed to slowly convert to positive in a high rate of dogs, in the absence of seroconversion. Thus, CS n-PCR technique can be a suitable marker for assessing Leishmania exposure in dogs as a non-invasive alternative to current serological and molecular tools, they say.

References

• Veterinary Parasitology, Volume 171, Issues 3-4, 4 August 2010, Pages 223-228