Use of a natural herbal-based feed additive containing isoquinoline alkaloids in newborn calves with cryptosporidiosis

Cryptosporidium infections are one of the most prevalent causes of diarrhea in calves and considered to be one of the major sources of economic loss in livestock production. A global trend is currently underway, in identifying natural and sustainable alternatives to support animal husbandry and production. Isoquinoline alkaloids are known for their anti-inflammatory, antimicrobial, and antioxidant properties in the promotion of gut health. Thus, an experiment was designed to evaluate the effects of natural, herbal-based feed isoquinoline alkaloids to support calves experimentally inoculated with Cryptosporidium parvum. Twenty-six calves were randomly divided into control (CN) (n = 13) and treatment (SG) (n = 13) groups. The SG group received 5 g of feed additive in every milk feeding from 1 to 21 days of age. The CN group received milk without any additives. All calves were orally inoculated on the third day of life with 1 × 10⁶Cryptosporidium parvum oocysts. The animals were evaluated daily, from 3 to 30 days of age, for the occurrence, duration, and intensity of diarrhea. Calves with a base deficit of ≥ 9 mEq/L were hydrated to aid recovery. The SG calves showed a higher average weight gain between 14 and 21 days of age, without mortality and with reduced intensity and duration of diarrhea. In contrast, calves in the CN group showed more serious acid-base disorders, required more hydration support, and had a mortality rate of 15.4 %. These results showed that calves supplemented with isoquinoline alkaloids had decreased intensity and duration of symptoms, reduced requirement for supportive therapy, and prevented mortality among animals.

Identification of a vertically transmitted strain from Anaplasma marginale (UFMG3): Molecular and phylogenetic characterization, and evaluation of virulence

Bovine anaplasmosis is a disease caused by the intraerythrocytic rickettsia species Anaplasma marginale and results in great economic losses in tropical and subtropical regions. Vertical transmission is an important phenomenon that contributes to the persistence of different strains of the agent within the same herd. The identification of new strains and genetic characterization studies are essential to understanding their epidemiology and virulence and for vaccine development. The aim of this study was to perform molecular and phylogenetic characterizations of a new vertically transmitted strain from A. marginale and to evaluate its virulence by experimental inoculation of rickettsia-free calves. Thirty newborn Holstein calves were subjected to molecular tests for the detection of A. marginale, Babesia bovis and Babesia bigemina. Calves positive for A. marginale (n=3) were splenectomized and monitored for the clinical manifestations of anaplasmosis. Blood samples from one of the calves that presented rickettsemia of 42.8% and spontaneous recovery of clinical parameters were used for molecular and phylogenetic characterization (msp1a gene), and inoculum production was used for the evaluation of virulence. This strain was identified as UFMG3. Three tandem repeat forms (13 and MGI19) were identified from the analysis of the msp1a gene, in which the form MGI19 appeared twice. Analysis of these repeats revealed the presence of the sequences QASTSS and SSASGQQQESS and of aspartic acid (D) at position 20 of both repeats. Phylogenetic analysis showed a close relationship among the UFMG3, MGI19 and UFMG2 strains. For virulence evaluation, six Holstein calves were inoculated intravenously with 2×10(7)A. marginale UFMG3-infected erythrocytes. The calves showed maximum rickettsemia of 5.1%, a moderate decrease in packed cell volume and spontaneous recovery of clinical parameters without the need for treatment. The results of experimental inoculation suggest that the strain A. marginale UFMG3 has low virulence and potential application for use as a live vaccine against A. marginale.

Genetic diversity and molecular phylogeny of Anaplasma marginale isolates from Minas Gerais, Brazil

Anaplasma marginale (Rickettsiales: Anaplasmataceae), a tick-borne pathogen of cattle, is endemic in tropical and subtropical regions of the world, and many isolates of A. marginale may occur in a given geographic area. Phylogenetic relationships have been reported for A. marginale isolates from the US using gene and protein sequences of MSP1a and msp4. These studies demonstrated that msp4 sequences, but not MSP1a DNA or protein sequences, provide phylogeographic information and also that MSP1a sequences are highly heterogeneous among A. marginale populations. However, little information is available on the genetic diversity of A. marginale isolates from other regions of the world. The present study was undertaken to examine genetic variation among 10 isolates of A. marginale obtained from infected cattle in the State of Minas Gerais, Brazil, where A. marginale is endemic. Neighbor-joining analysis of msp4 sequences of Brazilian and New World isolates of A. marginale from Argentina, Mexico and the US provided bootstrap support for a Latin American clade. The sequences of the MSP1a repeats of four Brazilian isolates of A. marginale were compared to sequences of Latin American and US isolates. The MSP1a repeated sequences of Latin American isolates of A. marginale had nine repeat forms, alpha-phi, which have not been reported previously in North American isolates of A. marginale. Furthermore, the repeated forms tau, sigma and mu were only present in the Brazilian isolates. The results demonstrated that the genetic heterogeneity observed among isolates of A. marginale is common in endemic areas, independent of the predominant tick vector and is consistent with previous studies in which msp4 provided phylogeographic information about A. marginale isolates, while MSP1a was found not to be a useful marker for phylogeographic characterization of A. marginale isolates.

Natural infection of calves by Anaplasma marginale in dairy herds of the Metalúrgica Region, Minas Gerais

The dynamic of natural infections by Anaplasma marginale in calves was evaluated during a period of one year on two farms located in the Metalúrgica Region, State of Minas Gerais, Brazil. Blood samples were collected weekly for rickettsemia and packed cell volume (PCV) determination. The animals born from March to July suffered the infection in October and November, independently of their age, whilst calves born from September to December acquired the infection during the first days of life. These animals presented patent rickettsemia from 30 days of life. During the patent period PCV decreased after one week of infection, ranging from 20 to 23%. It was concluded, that in the region studied, the transmission of A. marginale is influenced by climatic conditions, and that calves born during the dry season are more likely to acquire the infection when they are exposed to high transmission levels during the subsequent raining season.