Diagnostic, Clinical and Epidemiological aspects of dairy cows naturally infected by Trypanosoma vivax in the states of Pernambuco and Alagoas, Brazil

Abstract

Trypanosoma vivax is the most pathogenic hemoparasite of ruminants, causing huge economic losses to the producer when prevalent in the herd. This study aims to characterize the trypanosomiasis in naturally infected cattle in order to assess the clinical findings, epidemiological risk factors, and diagnosis of this disease in outbreaks occurring in the states of Pernambuco and Alagoas, northeastern Brazil. For this purpose, historical and clinical examinations, blood collection and clinical monitoring were performed in 109 animals presenting illness for a period of one year. The main clinical findings were fever, apathy, anorexia, diarrhea, progressive weight loss, lymphadenopathy, pale mucous, incoordination, aggressiveness, abortion, decrease in milk production, and high mortality. Out of 109animals, 94% (103/109) were seropositive to Trypanosoma vivax by ELISA, 92% (100/109) were seropositive for IFAT, 15% (17/109) were positive in conventional PCR assay based on the cathepsine L gene, and 9% (10/109) showed the presence of Trypanosoma vivax trypomastigotes in stained-blood smears. In 13 samples, blood counts revealed that 69.23% (9/13) showed normocytic normochromic anemia and 53.84% (7/13) had leukocytosis, in 46.15% (6/13) neutrophilia and regenerative left shift. In 72 samples, the hematocrit, plasma protein, and fibrinogen were also examines. The hematocrit presented an average of 22% (10% to 37%), plasma protein a mean value of 7.55 g/dl (5.4 g/dl to 10.0 g/dl), and plasma fibrinogen a mean value of 700mg/dl (200mg/dl to 1600mg/dl). The sequencing of DNA samples revealed 100% identicalness to Trypanosoma vivax by BLAST analysis. The main factors involved in the spread of the disease were: the ingress of animals without prior tests and quarantine into the properties, application of oxytocin with shared needles contaminated by blood at the time of lactation, and the restriction of the disease in the lactation herd. The transmission of Trypanosoma vivax occurred through the sharing of needles among lactating animals during application of oxytocin after the entry of carrier animals in the herd. Serological tests demonstrated a high rate of seropositive animals, however, conventional PCR and blood smears revealed a low positive rate because the animals were already being treated with trypanocid drugs. It is concluded that trypanosomiasis is a disease to be considered in the cattle regions studied as the cause of outbreaks. Hygiene and security actions should be taken during the administration of oxytocin in lactating cows. In fact, this practice, when performed using shared needles and without disinfection, is the main risk factor in the transmission of trypanosomiasis in dairy herds among regions where the disease is prevalent, increasing the challenge of reinfection of animals.

Diseases with neurological manifestations diagnosed in cattle in the hospital routine: a retrospective epidemiological study (2009-2019)

“…The acquisition of adult animals from endemic regions justifies the higher occurrence of this disease in this category. This condition may have contributed both to the entry of the parasite into local properties and to the dissemination of the parasite between animals of the same herd, as already widely mentioned in the literature (91,92,96) . However, in Paraiba, outbreaks of the disease in cattle coincided with an increase in the number of vectors (90,94) .…”

Serological occurrence for tick-borne agents in beef cattle in the Brazilian Pantanal

“…In Brazil, the expanding geographic distribution of T. vivax has resulted from the livestock moving between endemic regions and those where the conditions are favorable (climate favorable to hematophagous dipterans, animals lacking prior immunity to the parasite, and the permanent practice of sharing blood-contaminated needles [fomites] during vaccination and application of oxytocin) (Cadioli et al, 2012;Bastos et al, 2017;Andrade Neto et al, 2019). The results showed that cows are significantly more exposed to T. vivax compared to calves, which may be related to the longer period in contact with hematophagous mechanical vectors and fomites (especially due to shared needles).…”

Enfermidades com manifestações neurológicas diagnosticadas em bovinos na rotina hospitalar: estudo epidemiológico retrospectivo (2009-2019)

“…A aquisição de animais adultos de regiões endêmicas, justifica a maior ocorrência desta enfermidade nessa categoria. Essa condição pode ter contribuído tanto para a entrada do parasita nas propriedades locais, como para a disseminação do parasita entre animais do mesmo rebanho, assim como já é amplamente citado na literatura (91,92,96) . Entretanto, na Paraíba surtos da doença em bovinos coincidiram com o aumento no número de vetores (90,94) .…”