Visceral leishmaniasis in a recent transmission region: 27.4% infectivity rate among seronegative dogs

Abstract

American visceral leishmaniasis (VL) is a parasitic disease whose main domestic reservoir in the urban environment is dog and is considered one of the most important zoonoses in the context of public health. Serological tests are typically used for the diagnostic screening of the disease. This study aimed to analyse the performance of different methodologies used in the diagnosis of VL in dogs sampled from a recent transmission area. The sample consisted of 52 dogs separated into groups based on the absence and presence of clinical signs of VL. The following serological techniques were carried out: the DPP® rapid test (RT), the ALERE® RT and an RT and immunoenzymatic assay with a recently developed protein (rKDDR-plus). In addition, molecular techniques were carried out with conjunctival swabs, and bone marrow aspirate samples and parasitological samples were obtained directly from bone marrow aspirates. It was concluded that 27.4% of seronegative dogs were infected, but the serological tests, used as screening tests, showed unsatisfactory sensitivity results (average: 51.2%) for dogs without clinical signs. It was suggested that polymerase chain reaction with conjunctival swabbing be used as a screening test for dogs without clinical signs, as this is a non-invasive collection technique with high-sensitivity values.

Detection of multiple circulating sandflies species and investigation of dogs and vectors naturally infected with Leishmania in the city of Ribeirão Vermelho, southeastern Brazil

“…False-negative results are high when a screening test presents a relatively low sensitivity value. In this same study, carried out in Lavras, a municipality adjacent to Ribeirão Vermelho, Gondim et al (2022) found that more than half of the infected dogs did not display clinical signs characteristic of VL and were no longer detected by the screening tests. This finding is particularly important since dogs without clinical signs can present high transmissibility and potential for maintenance and dissemination of the parasite (Tolezano et al 2007).…”

“…It is still important to emphasize that the screening tests recommended by the "Ministério da Saúde" provide heterogeneous data and may present false negatives, even though these tests have high sensitivity. Gondim et al (2022) found low sensitivity in immunochromatographic tests used for screening. False-negative results are high when a screening test presents a relatively low sensitivity value.…”

Determination of the effect of collars containing 10% w/w imidacloprid and 4.5% w/w flumethrin (Seresto®) on the incidence of Leishmania and other canine vector-borne pathogen infections in Greece

“…Since these 16 dogs tested negative in all analyses other than the test on the conjunctival swab in the follow-up period, we ran a second statistical analysis excluding all dogs of this household. Reverse transcription-qPCR (qRT-PCR) on conjunctival swabs has proven to be a very sensitive non-invasive technique to screen dogs for leishmaniosis, as it has the potential to detect infection earlier than if it were performed on other tissues, even before any symptoms become evident [ 21 – 23 ]. However, it has been suggested that a positive result only by qRT-PCR on conjunctival swabs, in the absence of a positive result with any other diagnostic test or the presence of any clinical sign, should be considered with caution [ 24 ].…”