Identification of Leishmania spp. promastigotes in the intestines, ovaries, and salivary glands of Rhipicephalus sanguineus actively infesting dogs

Quantitative Detection of Leishmania in Rhipicephalus microplus and Amblyomma sabanerae in the Peruvian Amazon Basin

Leishmaniasis is a disease of public importance with a complex transmission cycle. A quantitative PCR was developed by using the small subunit of the ribosomal RNA gene (SSU rRNA) as a DNA target, which is conserved in all Leishmania species. A TaqMan ^® probe was designed to have a high specificity. In all, 22 out of 23 (95.7%) ticks classified as R. microplus tested positive for Leishmania sp. The quantification was between 34.1 and 2197.1 parasites per tick in a range of 12 to 769 fg/uL. In addition, 9 out of 10 (90%) ticks classified as Amblyomma sabanerae tested positive for Leishmania sp. The quantification was between 448.6 and 5428.6 parasites per tick in a range of 157 to 1900 fg/µL. Leishmania sp. was identified in very high percentages in Rhipicephalus microplus and Amblyomma sabanerae from wild Pecari tajacu and Chelonoidis denticulata, in quantities of 34.1 and 5428.6 parasites per arthropod, and this could suggest that the ticks were parasitized by sucking blood from the animals from which they were collected. This is the first report about Leishmania parasites found in wild Rhipicephalus microplus and Amblyomma sabanerae, adding new information about the distribution and epidemiology of the parasite in sylvatic areas.

Detection of Leishmania sp. kDNA in questing Ixodes ricinus (Acari, Ixodidae) from the Emilia-Romagna Region in northeastern Italy

To date, sand flies (Phlebotominae) are the only recognized biological vectors of Leishmania infantum, the causative agent of human visceral leishmaniasis, which is endemic in the Mediterranean basin and also widespread in Central and South America, the Middle East, and Central Asia. Dogs are the main domestic reservoir of zoonotic visceral leishmaniasis, and the role of secondary vectors such as ticks and fleas and particularly Rhipicephalus sanguineus (the brown dog tick) in transmitting L. infantum has been investigated. In the present paper, the presence of Leishmania DNA was investigated in questing Ixodes ricinus ticks collected from 4 rural areas included in three parks of the Emilia-Romagna Region (north-eastern Italy), where active foci of human visceral leishmaniasis have been identified. The analyses were performed on 236 DNA extracts from 7 females, 6 males, 72 nymph pools, and 151 larvae pools. Four samples (1.7%) (i.e., one larva pool, 2 nymph pools, and one adult male) tested positive for Leishmania kDNA. To the best of our knowledge, this is the first report of the presence of Leishmania kDNA in questing I. ricinus ticks collected from a rural environment. This finding in unfed larvae, nymphs, and adult male ticks supports the hypothesis that L. infantum can have both transstadial and transovarial passage in I. ricinus ticks. The potential role of I. ricinus ticks in the sylvatic cycle of leishmaniasis should be further investigated.

Canine visceral leishmaniasis and Rhipicephalus sanguineus: evaluation and comparison of classical techniques

The aim of this study was evaluating the association and correlation between the diagnostics tests used for Leishmania spp. detection in dogs and ticks. We evaluated 99 dogs and 990 Rhipicephalus sanguineus. In dogs, we used bone marrow aspirates and lymph node fine-needle aspiration biopsy (FNAB) for direct parasitological examinations and real time-polymerase chain reaction (RT-PCR) and collected blood samples for enzyme-linked immunosorbent assays (ELISA). In ticks, two laboratory techniques [immunohistochemistry to lipophosphoglycan (IHC) and RT-PCR] were performed in the intestine, ovaries and salivary glands. With respect to the measurement of diagnostic performance in dogs, lymph node RT-PCR proved to be the best test followed by ELISA and bone marrow RT-PCR. In ticks, intestine IHC were considered as a gold standard for diagnosis of leishmaniasis with intestinal RT-PCR being the best diagnostic test. To arrive at the correlation between laboratory techniques for dogs and their ticks, we evaluated the diagnostic test used for dogs with tests performed in R. sanguineus, which used lymph node FNAB as the gold standard. The intestine IHC technique showed strongest association. We demonstrated that the best tissue for Leishmania spp. detection in dogs was the lymph node and the intestine in case of ticks. As for laboratory techniques, the isolated analysis of each species presented a strong agreement between immunohistochemistry and RT-PCR when compared to its gold standard. In addition, we concluded that the immunohistochemistry of ticks' intestines was a better technique for diagnosing Leishmania spp. in R. sanguineus, thereby showing almost perfect correlation with the lymph node FNAB.

High seroprevalence and associated factors for visceral leishmaniasis in dogs in a transmission area of Paraíba state, Northeastern Brazil

Dogs have been implicated as main reservoirs for visceral leishmaniasis (VL) in urban areas. Therefore, studies on this species provide important data for public health. Thus, the objective of the present study was to ascertain the seroprevalence of canine VL (CVL) and the associated factors in the Brejo Paraibano microregion, northeastern Brazil. A total of 409 dogs were sampled from the eight municipalities of the microregion: Alagoa Grande, Alagoa Nova, Areia, Bananeiras, Borborema, Matinhas, Pilões and Serraria. The diagnosis of CVL was made using an enzyme-linked immunosorbent assay (ELISA S7®), through which the prevalence observed was 29.3%. By robust Poisson regression analysis two factors were associated with seroprevalence: illiterate/incomplete elementary owner's education level (prevalence ratio = 1.57; 95% CI = 1.05-2.34; p-value = 0.027) and tick infestation (prevalence ratio = 1.82; 95% CI = 1.27-2.61; p-value = 0.001). It is concluded that the seroprevalence of CVL in the Brejo Paraibano microregion is high. The factors associated with seroprevalence indicated the importance to develop socioeducational actions on the population, and the finding that tick infestation was associated with seroprevalence shows that there is a need for investigation regarding the role of ticks in the epidemiology of CVL.

Prevalence of Ehrlichia canis (Rickettsiales: Ehrlichieae) DNA in Tissues From Rhipicephalus sanguineus (Acari: Ixodidae) Ticks in Areas Endemic for Canine Monocytic Ehrlichiosis in Brazil

Canine monocytic ehrlichiosis (CME) is a disease caused by the obligate intracellular bacterium Ehrlichia canis. Tropical lineages of Rhipicephalus sanguineus ticks play an essential role in the transmission of this pathogen. The aim of the present study was to evaluate the prevalence of E. canis DNA in tissue from R. sanguineus ticks in areas endemic for CME in Brazil and quantify levels of E. canis DNA in dissected tissues from these samples. A total of 720 ticks were collected from 72 dogs (36 dogs from the city Araçatuba in São Paulo state and 36 from Campo Grande in the state of Mato Grosso do Sul). Ticks were dissected to collect the guts, ovaries and salivary gland. A quantitative polymerase chain reaction (qPCR) targeting the disulphide bond formation (dsb) protein gene was performed to quantify the level of E. canis infection. The E. canis dsb-qPCR assay was positive for 31.9, 10, and 15.2% of the gut, ovary, and salivary glands, respectively. The average gut, ovary, and salivary gland bacterial load estimated by qPCR was 1.21 × 103, 2.60 × 103, and 4.92 × 103 gene copies/µl, respectively. This is the first report of E. canis DNA in ovaries of R. sanguineus ticks parasitizing dogs in these CME-endemic areas. These observations raise the possibility of E. canis trans-ovarial transmission.

Real-time PCR applications for diagnosis of leishmaniasis

Leishmaniasis is a vector-borne disease caused by many Leishmania species, which can infect both humans and other mammals. Leishmaniasis is a complex disease, with heterogeneous clinical manifestations ranging from asymptomatic infections to lesions at cutaneous sites (cutaneous leishmaniasis), mucosal sites (mucocutaneous leishmaniasis) or in visceral organs (visceral leishmaniasis), depending on the species and host characteristics. Often, symptoms are inconclusive and leishmaniasis can be confused with other co-endemic diseases. Moreover, co-infections (mainly with HIV in humans) can produce atypical clinical presentations. A correct diagnosis is crucial to apply the appropriate treatment and the use of molecular techniques in diagnosis of leishmaniasis has become increasingly relevant due to their remarkable sensitivity, specificity and possible application to a variety of clinical samples. Among them, real-time PCR (qPCR)-based approaches have become increasingly popular in the last years not only for detection and quantification of Leishmania species but also for species identification. However, despite qPCR-based methods having proven to be very effective in the diagnosis of leishmaniasis, a standardized method does not exist. This review summarizes the qPCR-based methods in the diagnosis of leishmaniasis focusing on the recent developments and applications in this field.