The fucose-mannose ligand-ELISA in the diagnosis and prognosis of canine visceral leishmaniasis in Brazil.

Abstract

Abstract. The fucose-mannose ligand (FML)-ELISA assay showed a sensitivity of 100% and a specificity of 100% in diagnosis of canine visceral leishmaniasis (CVL) (kala-azar) in sera from naturally infected dogs from São Gonçalo do Amaranto, Rio Grande de Norte, Brazil. The overall prevalence of antibodies to Leishmania in the endemic area was 23% (79 of 343). Seroreactivity detected by a Leishmania chagasi immunofluorescent (IF) assay was much lower (2.9%) and similar to the percentage of dogs with kala-azar symptoms (2.6%). Twenty-one of 21 asymptomatic, FML-seropositive animals died of kala-azar in a period ranging from 0 to 6 months after diagnosis. The predictive value was 100% for the FML-ELISA, 43% for an L. mexicana ELISA, and 24% for the L. mexicana and L. chagasi IF assays, respectively. In experimentally infected dogs, all assays detected seropositivity between 90 and 120 days after infection. Since the current strategy for control of CVL is based on detection and destruction of infected dogs, the highly predictive, sensitive, and specific FML-ELISA represents a useful tool for field control of the disease.Zoonotic visceral leishmaniasis (ZVL) is one of the most important emerging diseases. 1 Its etiologic agent, (Leishmania chagasi or L. infantum) is introduced into the domestic cycle when infected foxes visit houses to scavenge poultry. Peridomestic sand flies acquire the parasite by feeding on the skin of foxes and transmitting it to dogs. The subsequent transmission to humans causes human visceral leishmaniasis (kala-azar), a severe disease that is lethal if not treated soon after the onset of symptoms. About 500,000 human cases of kala-azar are recorded annually worldwide. The current strategy for control of ZVL, as recommended by the World Health Organization, is based on detection and destruction or treatment of infected dogs and vector control. 1 The control of visceral leishmaniasis in northeastern Brazil involves the detection of infected dogs by serologic analysis using an immunofluorescent (IF) assay and elimination of seropositive dogs. 2 Seropositivity detected by the IF assay usually shows a good correlation with parasitologic evidence of infection. 2-4 However, due to its low sensitivity, this method underestimates the true prevalence of canine infection. More recently, an ELISA, 5 a dot-ELISA, 6 Western blotting, 7 rapid immunochromatographic tests, 8 and DNA molecular tools 2,9 have also been compared with conventional serology and proposed as alternative methods. No information is available concerning the predictive value of these tests. However, it is known that in human and canine kala-azar, antibodies to Leishmania appear in the circulation soon after infection, leading to an early subclinical period. 10 The early detection of infected dogs in the field could improve the control program since it would identify dogs that are still subclinical but already infective for sand flies. 3 We have recently tested the diagnostic and predictive value of the fucose-mannose ligand (FML)-ELISA f...

Specific Serodiagnosis of Canine Visceral Leishmaniasis Using Leishmania Species Ribosomal Protein Extracts

“…Palatnik-de-Sousa et al (40) have described the protective effect of the fucose-mannose ligand vaccine, like the Leishmune vaccine, against CVL. As expected with the use of saponin adjuvants, the Leishmune vaccine induces a strong humoral immune response soon after the complete vaccination is provided (9). Therefore, an indistinct IgGmediated anti-L. chagasi immune response is detected in Leishmune-vaccinated dogs, and that response is indistinct from that due to natural infection with L. chagasi.…”

“…However, due to the high degree of variability in the humoral responses to different parasite antigens observed in infected dogs (24,42), the efficient diagnosis of CVL based on recombinant proteins may require a mixture of recombinant proteins or the use of chimerical proteins containing several nonrelated parasite antigens (7,42,49). The specific diagnosis of CVL can also be developed by using preparations purified from the parasite (6,9) or crude parasite fractions analyzed by Western blotting (1,20).…”

Cross-Protective Efficacy of a ProphylacticLeishmania donovaniDNA Vaccine against Visceral and Cutaneous Murine Leishmaniasis

“…The two last species are considered very closely related (28). L. donovani FML is recognized by sera from kala-azar human and canine patients infected with L. chagasi with 100% sensitivity and 96 to 100% specificity (7,38). Sera from human and canine patients infected with L. infantum also react with FML in ELISAs (C. B. Palatnik de Sousa et al, unpublished results), indicating that this antigen can give a strong cross-reactivity with all of the species of the donovani complex.…”

Impact of canine control on the epidemiology of canine and human visceral leishmaniasis in Brazil.

“…53 The investigators concluded that the current FNS program based on IF screening of blood eluates is eliminating only 46% of the infected dogs. 53 We recently showed that when analyzed by the FML-ELISA (100% sensitivity and specificity for canine VL), 54 the positivity rate was 70.9% in sera, and 43.6% and 47.7% in eluates transported at Ϫ10ЊC or 25ЊC, respectively (Borja-Cabrera GP and others, unpublished data). Differences between results obtained in sera samples or eluates were highly significant (P Ͻ 0.005).…”

“…There is more experimental evidence supporting the usefulness of canine control using serologic analysis and dog elimination than against it. The efficacy of these control measures would be improved by the use of available, more sensitive serologic tests 51,54,57,58 and a more profound knowledge of the time-space distribution and evolution of VL in Brazil. It is important to note that important canine control campaigns have been conducted regularly in Brazil since 1981 with the support of the World Health Organization.…”