Frequency of co-seropositivities for certain pathogens and their relationship with clinical and histopathological changes and parasite load in dogs infected with Leishmania infantum

Abstract

In canine leishmaniosis caused by the protozoan Leishmania infantum, little is known about how co-infections with or co-seropositivities for other pathogens can influence aggravation of this disease. Therefore, the objectives of this study were to evaluate the frequency of co-infections with or co-seropositivities for certain pathogens in dogs seropositive for L. infantum and their relationship with clinical signs, histological changes and L. infantum load. Sixty-six L. infantum-seropositive dogs were submitted to clinical examination, collection of blood and bone marrow, culling, and necropsy. Antibodies against Anaplasma spp., Borrelia burgdorferi sensu lato, Ehrlichia spp. and Toxoplasma gondii and Dirofilaria immitis antigens were investigated in serum. Samples from different tissues were submitted to histopathology and immunohistochemistry for the detection of Leishmania spp. and T. gondii. Quantitative real-time PCR was used to assess the L. infantum load in spleen samples. For detection of Coxiella burnetii, conventional PCR and nested PCR were performed using bone marrow samples. All 66 dogs tested positive for L. infantum by qPCR and/or culture. Fifty dogs (76%) were co-seropositive for at least one pathogen: T. gondii (59%), Ehrlichia spp., (41%), and Anaplasma spp. (18%). Clinical signs were observed in 15 (94%) dogs monoinfected with L. infantum and in 45 (90%) dogs co-seropositive for certain pathogens. The L. infantum load in spleen and skin did not differ significantly between monoinfected and co-seropositive dogs. The number of inflammatory cells was higher in the spleen, lung and mammary gland of co-seropositive dogs and in the mitral valve of monoinfected dogs. These results suggest that dogs infected with L. infantum and co-seropositive for certain pathogens are common in the region studied. However, co-seropositivities for certain pathogens did not aggravate clinical signs or L. infantum load, although they were associated with a more intense inflammatory reaction in some organs.

Atypical Lesions in Canine Leishmaniosis: Description of New Cases

“…In some cases, atypical lesions have only been demonstrated after studying atypical clinical signs and adequate response to treatment after diagnosis [ 8 , 25 , 26 ]. Additionally, lesions in natural cases in endemic regions can be modulated by concurrent infections [ 27 ].…”

Epidemiologic, Clinical and Immunological Consequences of Co-Infections during Canine Leishmaniosis

“…T. gondii is globally distributed, and there is a high burden of infection in mammals worldwide, thus dogs in Leishmania -endemic areas are exposed [ 40 , 41 ]. A Brazilian study of 66 L. infantum -seropositive dogs found 59% were co-seropositive for T. gondii [ 130 ]. In another study from Brazil, 8 out of 14 L. infantum -infected dogs were co-seropositive for T. gondii [ 195 ].…”

“…In southern Portugal, 8.3% of 230 dogs were co-infected with L. infantum and D. immitis [ 43 ]. Additional studies found no association between D. immitis and clinical CanL in dogs [ 20 , 130 ].…”

“…As an example for Leishmania , a study by da Costa Oliveira et al (2021) found 89.4% of 66 Brazilian dogs identified by serology had a positive result for Leishmania spp. by either immunohistochemistry or culture [ 130 ]. Different specimens may also be used for diagnostic testing, such as lymph node or spleen aspirates, although the majority of testing uses blood or sera samples due to ease of blood collection compared to more invasive techniques [ 85 ].…”

“…As a result, there may be inadequate or underreporting of particular signs for various co-infections. According to da Costa Oliveira et al (2021), clinical signs were not made worse by co-infections with T. gondii , Ehrlichia spp., or Anaplasma spp., although 91% of the 66 dogs had clinical CanL with the most common clinical signs being splenomegaly, onychogryphosis, and furfuraceous desquamation of skin [ 130 ]. Additionally, contribution of clinical signs to a specific pathogen is nearly impossible for a dog with these co-infections, especially since these infections often have similar physical exam findings and similar hematologic and serum chemistry findings.…”