Predominant risk factors for tick-borne co-infections in hunting dogs from the USA.

BACKGROUND: Both incidence and geographical range of tick-borne disease has increased across the USA. Similar to people, dogs are hosts for Anaplasma spp., Babesia spp., Ehrlichia spp. and Borrelia burgdorferi. Dogs also share our homes and beds, making them both a sentinel for the ticks in our backyards but also increasing our exposure to ticks. Measures to better track, prevent, and/or treat tick-borne diseases in companion animals can lead to better control and prevention of human tick-borne disease. This study identifies demographic and co-infection risk factors for canine seropositivity to tick-borne infections in a cohort of hunting dogs across the USA. RESULTS: Human patterns of tick-borne disease co-infection in the USA have been predominantly driven by the geographical distribution of the tick vector. Dogs who tested seropositive for Anaplasma spp. were 1.40 times more likely (P = 0.0242) to also test seropositive for Babesia spp. and vice versa (1.60 times more likely, P = 0.0014). Dogs living in the West had 5% lower risk (P = 0.0001) for Ehrlichia spp. seropositivity compared to other regions. Controlling for age and Anaplasma spp. seroprevalence, dogs in all three other regions were 2.30 times more likely (P = 0.0216) to test seropositive for B. burgdorferi than dogs in the West. Dogs seropositive for B. burgdorferi were 1.60 times more likely (P = 0.0473) to be seropositive for Anaplasma spp. CONCLUSIONS: Tick geographical distributions have a prominent impact on the regional distribution of hunting dog exposure to tick-borne diseases. Education concerning regional tick prevalence and disease risk is important for everyone, but particularly dog owners, regarding ticks in their region and protection from infection and co-infection of tick-borne pathogens as they travel or move with their dogs. Dogs are sentinel species for human exposure to ticks, and as such surveillance of canine tick-borne infections and understanding the probability that these infections might be seen together as co-infections helps predict emerging areas where people are more likely to be exposed as well.

Comorbid infections induce progression of visceral leishmaniasis.

BACKGROUND: Visceral leishmaniasis (VL) is a vector borne zoonotic disease endemic in humans and dogs in Brazil. Due to the increased risk of human infection secondary to the presence of infected dogs, public health measures in Brazil mandate testing and culling of infected dogs. Despite this important relationship between human and canine infection, little is known about what makes the dog reservoir progress to clinical illness, significantly tied to infectiousness to sand flies. Dogs in endemic areas of Brazil are exposed to many tick-borne pathogens, which are likely to alter the immune environment and thus control of L. infantum. RESULTS: A cross-sectional study of 223 dogs from an area of Natal, in the Rio Grande do Norte, Brazil, were studied to determine the association between comorbid tick-borne disease and Leishmania infection in this endemic area. The risk of Leishmania seropositivity was 1.68× greater in dogs with tick-borne disease seropositivity compared to those without (Adjusted RR: 1.68, 95% CI: 1.09-2.61, P = 0.019). A longitudinal study of 214 hunting dogs in the USA was conducted to determine the causal relationship between infection with tick-borne diseases and progression of VL. Hunting dogs were evaluated three times across a full tick season to detect incident infection with tick-borne diseases. A logistic regression model with generalized estimating equations to estimate the parameters was used to determine how exposure to tick-borne disease altered VL progression over these three time points when controlling for other variables. Dogs infected with three or more tick-borne diseases were 11× more likely to be associated with progression to clinical VL than dogs with no tick-borne disease (Adjusted RR: 11.64, 95% CI: 1.22-110.99, P = 0.03). Dogs with exposure to both Leishmania spp. and tick-borne diseases were five times more likely to die during the study period (RR: 4.85, 95% CI: 1.65-14.24, P = 0.0051). CONCLUSIONS: Comorbid tick-borne diseases dramatically increased the likelihood that a dog had clinical L. infantum infection, making them more likely to transmit infection to sand flies and people. As an important consequence, reduction of tick-borne disease exposure through topical or oral insecticides may be an important way to reduce progression and transmissibility of Leishmania infection from the canine reservoir to people.

Adesão leucocitária e MDA sérico em cães naturalmente infectados por Leishmania infantum / Leukocyte adhesion and MDA serum levels in naturally infected dogs by Leishmania infantum

O presente estudo avaliou o estresse oxidativo e a adesão de leucócitos (AL) em cães naturalmente infectados por Leishmania infantum. Foram utilizados cães saudáveis (CN = 10) e cães acometidos por leishmaniose visceral na forma sintomática (CS = 10), submetidos previamente a exames de imunofluorescência indireta (IFI), ensaio imunoenzimático (ELISA) e pesquisa do parasito em aspirados de medula óssea. Soro foi utilizado para avaliação de malondialdeído (MDA) no ensaio para espécies reativas ao ácido tiobarbitúrico (TBARS) e AL foi determinada pelo método da coluna de náilon em sangue em EDTA, heparina e citrato. Os dados de AL foram expressos em porcentagem e MDA em média ± desvio padrão, submetidos ao teste T de student não pareado (p < 0,05). Amostras em heparina apresentaram níveis mais elevados de AL no grupo CS (55,62%, p < 0,05) quando comparadas com EDTA e citrato (10,46% e 5,28%). Citrato e EDTA inibiram AL em cães doentes e saudáveis, enquanto a heparina preservou a AL. A proporção neutrofílica se apresentou reduzida nas amostras em heparina (85% para 67%, p <0,05) quando comparadas com citrato e EDTA, que por sua vez mantiveram-se estáveis (83% para 80%). Os níveis de MDA apresentaram-se mais elevados em CS (0,0117µM ± 0,002) quando comparado com CN (0,0057µM ± 0,001) (p <0,05). Estes dados dão suporte à conclusão de que na LVC ocorre elevação do estresse oxidativo e aumento da expressão das moléculas de adesão nos leucócitos, evidenciando resposta inflamatória sistêmica. A escolha do anticoagulante é importante para a implementação do ensaio de AL.

The present study evaluated the oxidative stress and leukocyte adhesion (LA) in dogs naturally infected by Leishmania infantum. Healthy dogs (HD = 10) and dogs affected by canine visceral leishmaniasis (CVL) in symptomatic form (SD= 10) were previously submitted to indirect immunofluorescence reaction (IIF), enzyme-linked immunosorbent assay (ELISA) and detection of parasites in bone marrow aspirates. Serum was used to assess malondialdeid (MDA) by thiobarbituric acid reactive species (TBARS) assay and AL was determined by nylon column method using whole blood stored in EDTA, citrate and heparin. AL data was expressed as percentage and MDA data as mean ± standard deviation, both submitted to the unpaired student's T test (p < 0.05). Heparin samples showed higher levels of AL in CS group (55.62 %, p < 0.05) when compared with EDTA and citrate (10.46% and 5.28%). Citrate and EDTA inhibit AL in healthy and sick dogs, while heparin preserved AL in both groups. Neutrophil proportion in heparin samples were lower (85% to 67%, p <0.05) compared with citrate and EDTA, which in turn remained practically unchanged (83% to 80%). MDA levels were higher in SD (0.0117µM ± 0.002) when compared to HD (0.0057µM ± 0.001) (p <0.05). These data support the conclusion that CVL induces oxidative stress enhance and leukocyte adhesion increase, indicating systemic inflammatory response. The choice of anticoagulant is an important decision for implementing LA assays.