Research note: Lateral transmission of Histomonas meleagridis in turkey poults raised on floor pens.

Histomoniasis is caused by the protozoa Histomonas meleagridis (HM) that are laterally transmitted among birds leading to high mortality in commercial flocks. This study tested an HM infection model assessing the lateral transmission of HM in turkey poults raised on floor pens. Day (d)-old female turkey poults (n = 320) were individually wing-tagged and allocated to one of four treatment groups (4 floor pens/group and 20 poults/pen) based on the percentage of poults inoculated with HM: 1) 10% (HM10); 2) 20% (HM20); 3) 30% (HM30); and 4) 40% (HM40). On d 9, seeder poults intracloacally received a 1 mL inoculum/bird containing ∼80,000 histomonads. Poults were individually weighed on d 0, 9, and 25 and feed intake recorded on per pen basis. On d 25, all birds were euthanized by cervical dislocation and ceca and liver were evaluated for HM lesions. Data were analyzed using JMP (Pro16) and significance (P ≤ 0.05) between treatments were determined by LSD test. Mortality was 7.63%, 12.5%, 21.58%, and 20.59%, while transmission rates from inoculated to non-inoculated birds were 62.5%, 57.5%, 92.43%, and 78.75% in HM10, HM20, HM30, and HM40 groups, respectively. Average daily feed intake was proportionally reduced with the increasing number of inoculated poults from HM10 to HM40. Average daily gain was significantly lower in HM30 and HM40 poults compared to those in HM10 and HM20 during the postchallenge period (d 10-25). Therefore, we herein report the successful lateral transmission of HM among turkey poults raised on floor pens. This research model closely resembles commercial field conditions and affords a much-needed platform for conducting relevant basic and applied research on histomoniasis in poultry.