Excretion of Histomonas meleagridis following experimental co-infection of distinct chicken lines with Heterakis gallinarum and Ascaridia galli

Abstract

Background Histomonosis is a severe re-emerging disease of poultry caused by Histomonas meleagridis, a protozoan parasite which survives in the environment via the cecal worm Heterakis gallinarum. Following infection, the parasites reside in the ceca and are excreted via host feces. In the present work, male birds of conventional broiler (Ross 308, R), layer (Lohmann Brown Plus, LB) and a dual-purpose (Lohmann Dual, LD) chicken line were infected with 250 embryonated eggs of Ascaridia galli and Heterakis gallinarum, respectively, with the latter nematode harboring Histomonas meleagridis, to investigate a co-infection of nematodes with the protozoan parasite in different host lines. Methods In weekly intervals, from 2 to 9 weeks post infection (wpi), individual fecal samples (n = 234) from the chickens were collected to quantify the excretion of H. meleagridis by real-time PCR and to determine the number of nematode eggs per gram (EPG) in order to elucidate excretion dynamics of the flagellate and the nematodes. This was further investigated by indirect detection using plasma samples of the birds to detect antibodies specific for H. meleagridis and worms by ELISA. The infection with H. meleagridis was confirmed by histopathology and immunohistochemistry to detect the flagellate in the cecum of representing birds. Results The excretion of H. meleagridis could already be observed from the 2nd wpi in some birds and increased to 100% in the last week of the experiment in all groups independent of the genetic line. This increase could be confirmed by ELISA, even though the number of excreted H. meleagridis per bird was generally low. Overall, histomonads were detected in 60% to 78% of birds with temporary differences between the different genetic lines, which also showed variations in the EPG and worm burden of both nematodes. Conclusions The infection with H. gallinarum eggs contaminated with H. meleagridis led to a permanent excretion of the flagellate in host feces. Differences in the excretion of H. meleagridis in the feces of genetically different host lines occurred intermittently. The excretion of the protozoan or its vector H. gallinarum was mostly exclusive, showing a negative interaction between the two parasites in the same host. Graphic abstract

Coinfection of the gut with protozoal and metazoal parasites in broiler and laying chickens

“…The clinical signs recorded in the current study were ruffled feathers, loss of weight, emaciation, paleness in the comb and wattles with different colors, watery droppings that varied from brownish, orange color, and hemorrhagic, drop in egg production, changes in external egg quality, and variable mortalities in the investigated farms. Our findings agree with those of Daş et al (2021) , who observed comparable symptoms in broiler hens infected with Histomonas meleagridis after experimental coinfection with Heterakis gallinarum and A. galli .…”

Fenbendazole resistance in Heterakis gallinarum, the vector of Histomonas meleagridis, on a broiler breeder farm in South Carolina

“…In a previous passage of this isolate, cecal cores, associated with histomoniasis, were seen in infected birds, and we observed that few or no worms were recovered from birds with cecal cores. This observation is consistent with results of a study that demonstrated a negative interaction between H. meleagridis and H. gallinarum within the ceca (22). Given this issue, we felt that it would be optimal to treat the birds early in the course of infection to limit confounding effects on worm numbers due to formation of cecal cores.…”

Histomonosis in Poultry: A Comprehensive Review

“…Although chickens were previously regarded as sub-clinically affected by histomonosis, outbreaks have occurred recently in broiler breeder and freerange flocks (76,77). Interestingly, recent research has indicated that H. meleagridis infection and replication are similar regardless of chicken genetic line, further suggesting that chickens may be asymptomatic or sub-clinically infected but not actually resistant to infection (78).…”

“…(89,(116)(117)(118)(119)(120). DNA presence does not necessarily indicate active infection; therefore, diagnosis of histomonosis is recommended to include microscopy to confirm presence of the protozoa (78,110,115). H. meleagridis conforms similarly to other trichomonad parasites in structure and division; close phylogenetic relationships to D. fragilis and Tritrichomonas foetus were identified based on gene sequencing analysis of β-tubulin and small subunit rRNA genes (40,(121)(122)(123).…”