Anin vitroattenuated strain ofHistomonas meleagridisprovides cross-protective immunity in turkeys against heterologous virulent isolates

Abstract

In the current study, cross-protective immunity induced by a well-defined clonal strain of Histomonas meleagridis, attenuated by prolonged in vitro cultivation against different clonal heterologous isolates of the same parasite was investigated. For this purpose, 86 turkey poults were assigned to groups consisting of 9-10 birds. Birds of four groups were vaccinated on their 1st day of life followed by re-vaccination on their 14th day of life when the remaining turkeys were left untreated. The challenge was performed using four strains of H. meleagridis that were isolated from chickens or turkeys from different outbreaks of histomonosis in Europe and three of them showed diversities in their genome. Hence, every strain used for the challenge was applied to a group of vaccinated and a group of non-vaccinated birds while birds of the negative control group were sham inoculated. Non-vaccinated birds suffered from severe histomonosis due to the challenge with fatalities reaching from 5 to 10 turkeys per group. Vaccinated birds did not contract clinical signs of the disease following challenge and the increase in weight was unaffected compared to birds of the negative control group. A significant difference in lesion scores was recorded between vaccinated and non-vaccinated groups, with very few instances of liver involvement in the former groups. Livers of vaccinated birds that were without recordable macroscopic lesions were also found negative by immunohistochemical investigation. According to the data obtained, the present study demonstrates, for the first time, the cross-protective capability of a tentative vaccine strain of H. meleagridis attenuated in vitro against heterologous virulent isolates of different origin.

Phytoncides in the prevention and therapy of blackhead disease and their effect on the turkey immune system

“…The action strategy aimed at countering H. meleagridis infection in poultry flocks mainly entails searching for effective preparations of plant origin and developing a vaccine. As indicated by research findings (29), experimental vaccination using in vitro attenuated H. meleagridis effectively protects turkeys from histomonosis and is safe to use, which recommends it as the most promising means of prevention of histomonosis in poultry for the future. However, numerous publications show that, despite satisfactory in vitro results, phytocompounds fail to produce promising effects in vivo in the fight against this flagellate (1,12,14,32).…”

“…This situation and the fact that biosecurity measures do not always prevent H. meleagridis introduction into a flock, infection (4), or ultimate disease outbreak, have forced a new approach to the problem of histomonosis prevention and treatment. That is why recent research focuses on various areas of disease control from the use of phytocompounds (1,12,31) to administration of vaccines (25,29). The presented study aims to assess the therapeutic and preventive efficacy of phytoncides contained in adiCox SOL PF (AdiFeed, Warsaw, Poland), a feed supplement for poultry, in a clinical case of histomonosis in a parent turkey flock, as well as to determine their effect on selected parameters of bird cell-mediated and humoral immunity.…”

PCR and serology confirm the infection of turkey hens and their resilience to histomonosis in mixed flocks following high mortalities in toms

“…In general, there are two genotypes of H. meleagridis based on the 18S rRNA gene, genotype 1 and genotype 2, with the latter occurring less frequently [13]. Only slight differences in pathogenicity of different clonal isolates within genotype 1 have recently been observed in an experimental study [27]. In comparison, Tyzzer [28] observed variations in virulence of naturally occurring histomonad strains.…”

Histomonosis in poultry: previous and current strategies for prevention and therapy

“…Further experiments in adult layers have shown that vaccinated birds can be protected from a severe drop in egg production caused by histomonosis (Liebhart et al, 2013b). Most recently, crossprotection by the mentioned attenuated clonal strain against genetically different isolates of H. meleagridis was demonstrated in turkeys (Sulejmanovic et al, 2016).…”