Fatal cases of Theileria annulata infection in calves in Portugal associated with neoplastic-like lymphoid cell proliferation

Abstract

This study was carried out to investigate fifteen cases of acute lethal infection of calves (≤ 4 months of age) by the protozoan parasite Theileria (T.) annulata in the south of Portugal. Calves developed multifocal to coalescent nodular skin lesions, similar to multicentric malignant lymphoma. Infestation with ticks (genus Hyalomma) was intense. Theileria was seen in blood and lymph node smears, and T. annulata infection was confirmed by isolation of schizont-transformed cells and sequencing of hypervariable region 4 of the 18S rRNA gene. At necropsy, hemorrhagic nodules or nodules with a hemorrhagic halo were seen, particularly in the skin, subcutaneous tissue, skeletal and cardiac muscles, pharynx, trachea and intestinal serosa. Histologically, nodules were formed by large, round, lymphoblastoid neoplastic-like cells. Immunohistochemistry (IHC) identified these cells as mostly CD3 positive T lymphocytes and MAC387 positive macrophages. A marker for B lymphocytes (CD79αcy) labeled very few cells. T. annulata infected cells in these nodules were also identified by IHC through the use of two monoclonal antibodies (1C7 and 1C12) which are diagnostic for the parasite. It was concluded that the pathological changes observed in the different organs and tissues were caused by proliferation of schizont-infected macrophages, which subsequently stimulate a severe uncontrolled proliferation of uninfected T lymphocytes.

Detection and phylogenetic characterization of Theileria spp. and Anaplasma marginale in Rhipicephalus bursa in Portugal

“…T. annulata is mainly transmitted by ticks of the genus Hyalomma; however, similarly to our study, R. bursa was also associated with the transmission of this pathogen in Tunisia (M'Ghirbi et al, 2010). In cattle, T. annulata is the causative agent of tropical theileriosis responsible for serious constraints on the animal health and productivity worldwide due to high morbidity and mortality (Branco et al, 2010;Doliveira et al, 1995). In Portugal, the presence of this tick-borne pathogen has already been reported in cattle during an acute lethal infection of calves highly infested by ticks of the genus Hyalomma (Branco et al, 2010), and during a survey conducted in asymptomatic cattle for detection of piroplasms (Gomes et al, 2013).…”

“…In cattle, T. annulata is the causative agent of tropical theileriosis responsible for serious constraints on the animal health and productivity worldwide due to high morbidity and mortality (Branco et al, 2010;Doliveira et al, 1995). In Portugal, the presence of this tick-borne pathogen has already been reported in cattle during an acute lethal infection of calves highly infested by ticks of the genus Hyalomma (Branco et al, 2010), and during a survey conducted in asymptomatic cattle for detection of piroplasms (Gomes et al, 2013). Nevertheless, we were not able to identify any study conducted in Portugal that has isolated T. annulata from R. bursa ticks.…”

Nucleolar Organizer Region Count, PCNA and Ki-67 Indices are Diagnostic Markers of Malignancy and Cell Proliferation Rate in Bovine Lymphosarcoma

“…Mitotic figures were present. Iwama et al [21] and Branco et al [22] observed similar histological features.…”

Population diversity of Theileria annulata in Portugal

“…In Portugal, the importance of theileriosis is becoming increasingly recognised (Branco et al, 2010;Silva et al, 2010) and a recent epidemiological study determined an increased prevalence in the south of the country. In a crosssectional study in Southern Portugal, around 30% of cattle were found to be infected within an area that represents around 50% of this country's cattle population .…”