R.equi dose titration study (Comparison of two preparations of R. equi 103+ strain)

FUMUSO E.; HERRERA M.; ROSSATI J.; QUINTEROS D.; ESTEIN S.M.; CERIANI C.

2011-08-01

2012-03-01

Sanidad animal-Enfer. infec. bacterianas

This study was divided into three chapters for the purpose of meeting the following objectives: To compare and determine the optimal challenge dose of R. equi103+ strain in foals of 42 days of age. A new batch of R. equi 103+ was prepared and needed to be tested prior to its use in further studies. Additionally, foals of 42 days of age were be challenged with an old batch of R. equi 103+. Clinical signs and disease outcomes in challenged foals were evaluated and compared between the two R. equi 103+ strain batch preparations. (b)To confirm the safety of a live attenuated R. equi MprB vaccine in a controlled experimental setting was evaluated in 4 foals, following a single challenge at 4 to 7 days after birth. (c)To evaluate Immunity induced of R. equi MprB vaccine (efficacy) on vaccinated foals through intrabroncheal challenged, at 42 days of age with 103+ virulent R. equi strain. For chapter (a) three batch of R.equi were tested 103+ strains identified as follows (1)Second New batch (2) second Old batch (3) Third Old batch received 9th March. This experimental study included 6 unbalanced experimental groups of foals (foals age ranging from 36 to 74 days at the time of challenge). Eleven foals were randomly assigned into each group and challenged with 25ml or 50 mL of PBS containing Colony Forming Units (CFU) per foal. After challenge, the animals were observed for 60 days and rectal temperatures, clinical signs, respiratory rate and fibrinogen values were measured and recorded. Lung ultrasonography to determine presence, size and distribution of lung abscesses was performed and results were recorded. Animals were declared sick if a foal exhibited one or more of the following 5 defined clinical signs of R. equidisease (lethargy, inappetence, increased respiratory rate, cough, respiratory distress) in addition to both fever and evidence of lung pathology.