Abrupt rises in mortality from highly pathogenic avian influenza (HPAI) can set off alarms at any poultry farm. Such was the case last year with an outbreak in a layer flock in Iowa.
Yuko Sato, DVM, at Iowa State University, reported that she received layer pullets from a facility that had seen acute, elevated mortality. The flock owner had observed weakness and lethargy. A rising number of birds had died over the 4 days prior to birds being sent for diagnosis, peaking at 77 in one day.
The problems occurred in the midst of a series of HPAI outbreaks in Iowa, meaning that it was an initial cause of concern, Sato told an audience at the 2023 Association of Avian Pathologists conference.
Early testing sheds telling light
The 10 birds were alive on arrival but moribund and emaciated. Sato conducted necropsies that showed nine of the 10 birds had no food in their gizzard. Two birds also showed cecal cores — accumulations of blood, tissue and oocysts.
Based on these observations, Sato suspected enteric coccidiosis, salmonellosis or histomoniasis. She and her team collected swabs and submitted them for quantitative PCR testing, to check for HPAI.
After the result came back negative, laboratory analysis showed necrosis of the mucosa, aggregations of bacteria and, most crucially for diagnosis, the presence of Histomonas protozoa and Heterakis spp. nematodes. Histomoniasis was the cause of the birds’ health issues — though in this case it was exacerbated by management issues.
“Feed lines were too high and birds starved out and consumed litter, increasing the chance of parasitic infection. There had also been past history of histomoniasis on this premises,” Sato said.
“The key learning for producers is not to wait to test birds. In this case, they certainly felt much better after HPAI was ruled out.”
Photo by Christopher Gannon, Iowa State University