Genetic resistance to Ascaridia galli infections in chickens.

Ascaridiosis is still a cause of economic losses in modern poultry production systems. Improving genetic resistance to this disease provides an attractive alternative for free-range organic poultry producers and will eventually reduce the extensive use of anthelmintic drugs. An experiment was conducted to compare resistance to Ascaridia galli infections in Lohman Brown (LB) and Danish Landrace (DL) chickens. A self-cure mechanism to A. galli infections was observed in both breeds. However, significantly higher worm burdens and egg excretion were seen in the DL compared to LB chickens during primary infection. This indicates that breeding for resistance to A. galli is possible in chickens.     

Molecular characterization of Ascaridia galli from Bangladesh and development of a PCR method for distinguishing A. galli from Heterakis spp.

We analyzed the nuclear ribosomal internal transcribed spacer (ITS) 1 and ITS2 sequences for Bangladesh isolates of Ascaridia galli, and we determined that the sequences were unreliable as molecular markers for distinguishing A. galli from other Ascaridia species, because the sequences showed high identity with that of A. columbae. However, the ITS1 sequences were available for designing PCR primers distinguishable between Ascaridia galli and Heterakis spp. Bangladesh isolates of A. galli constituted a monophyletic clade along with other geographical isolates in the cytochrome c oxidase subunit I (COI) phylogenetic tree, however, we could not clarify the phylogenetic relationships between A. galli and other Ascaridia spp., because their available sequences in GenBank were very few. The developed PCR method using DNA from A. galli and Heterakis spp. eggs would enable differential diagnosis of the individual infections in the future.     

An outbreak of histomoniasis in turkeys infected with a moderate level of Ascaridia dissimilis but no Heterakis gallinarum.

Histomoniasis was diagnosed in a commercial turkey flock. All morbidity and mortality occurred in one house. Birds exhibited lesions characteristic for histomoniasis, and the diagnosis was confirmed by histopathologic examination. Affected turkeys were infected with moderate levels of Ascaridia dissimilis but not Heterakis gallinarum. Compression smears of hepatic tissues showed typical histotrophic phase Histomonas meleagridis, whereas cecal smears exhibited large numbers of Trichomonas gallinarum. A challenge experiment was conducted in which turkey poults were placed on contaminated litter. Although histomoniasis was not reproduced in the experiment, the birds did become infected with low numbers of A. dissimilis.     

Precision, repeatability and representative ability of faecal egg counts in Heterakis gallinarum infected chickens

This study investigated whether a precise and repeatable quantification of Heterakis gallinarum egg excretion, which considerably reflects the actual worm burdens, can be achieved based on collection of the daily total amount of faeces from chickens. Three-week-old birds (N=64) were infected with 200 embryonated eggs of H. gallinarum, and placed into individual cages 3 wk after infection for 5 wk to collect daily faeces (N=2240). The total daily faeces was mixed and a randomly taken sample per bird was analyzed to estimate the numbers of eggs per gram of faeces (EPG) and total number of eggs excreted within 24h (EPD). A total of 235 daily faecal collections were randomly selected and further examined to determine between and within sample variations of EPG counts as a measure of precision. For this, two random faecal samples were taken from the daily produced faeces by a bird, and the EPG was determined for each of the samples (EPG1 and EPG2). The second faecal sample was analyzed once more to determine a parallel EPG2 count (EPG2a) of the suspended sample. Precision of an EPG count was defined as its relative closeness to the average of two EPG counts using a relative asymmetry index (Index(EPG)). At an age of 11 wk, i.e. 8 wk p.i. the birds were slaughtered and their worm burdens were determined. There were no significant differences between EPG1 and EPG2 (P=0.764) nor between EPG2 and EPG2a (P=0.700), suggesting that the differences between or within the samples were not different from zero. Correlations between EPG counts, as between and within sample coherences, were r=0.85 and r=0.86, respectively. Precision of EPG counts, as measured by Index(EPG), was not influenced by consistency (P=0.870) and total amount of faeces (P=0.088). However, concentration of eggs in faeces (mean EPG) had a significant effect on the precision of the EPG counts (P<0.001). Similar results were also observed for the within sample precision (Index(EPG2)). A segmented regression analysis indicated an abrupt change in the precision of EPG counts as the response to changing egg concentration in the examined faecal samples. The precision of analyses remarkably heightened up to a breakpoint with an EPG count of ≤ 617. A similar breakpoint was also determined for within sample precision (EPG2 ≤ 621). Moderate repeatabilities (R=0.49) for EPG and EPD were estimated in the first week of egg excretion, whereas the estimates were higher (R=0.67-0.84) in the following weeks. Correlations between number of female worms with daily measured EPG and EPD increased to an almost constant level (r ≥ 0.70; P<0.05) in a few days after the nematode excreted eggs and predominantly remained so for the rest of the sampling period. It is concluded that mixing daily total faeces provides samples with random homogenous distribution of H. gallinarum eggs. Precision of the EPG counts increases as the egg concentration in faecal sample increases. Egg excretion of H. gallinarum, quantified either as EPG or EPD, is highly repeatable and closely correlated with the actual worm burden of birds starting as early as in 5 th wk of infection.     

The effect of Plasmodium gallinaceum on a challenge infection with Ascaridia galli in chickens

The effect of a primary infection with the haemoparasite Plasmodium gallinaceum on the establishment of a challenge infection with the nematode Ascaridia galli in chickens was studied. Four groups were infected as follows. Group 1: inoculated intravenously with 10(6) P. gallinaceum-infected erythrocytes on day 0; group 2: orally infected with 500 embryonated A. galli eggs on day 10; group 3: infected with P. gallinaceum on day 0 and A. galli on day 10; and group 3: non-infected control birds. The results of this investigation demonstrates that a primary infection with P. gallinaceum in chickens alters the course of a subsequent infection with A. galli. Thus, an antagonistic effect was seen in which the malaria infection caused a significant reduction on the establishment of the nematode in concurrently infected animals.     

Host age only partially affects resistance to primary and secondary infections with Ascaridia galli (Schrank, 1788) in chickens

Two experiments were conducted to compare the effect of chickens' age on resistance to primary and secondary infections with Ascaridia galli. In Experiment I, three groups, each of 80 female Lohman Brown chickens, aged one day, one month, or four months were compared. Within each group, 54 chickens were infected orally with 500 embryonated eggs and 26 were kept as non-infected controls. Weights were recorded weekly and five chickens in each group were slaughtered every 2 weeks for worm counts. At week 10 post-infection, 17 of the infected chickens and 18 of the controls were challenged with 500 eggs. In a replicate experiment (Experiment II), 35 one-day-old and 53 one-month-old female Lohman Brown chickens were infected orally with 500 A. galli eggs. Weights and fecal egg counts were recorded every week and infected chickens were necropsied every two weeks for determination of the worm burden. Chickens infected at one month of age excreted significantly fewer A. galli eggs when measured at 14 weeks of inoculation. The worms recovered from the one-month-old age group were significantly shorter than those from the chickens infected at one day of age in the first experiment. Worm burden and female fecundity values, however, were not significantly different between age groups in both Experiments I and II. Weight gains of infected chickens were not significantly different from the controls' and only a few chickens exhibited occasional slight diarrhea in both experiments. The results from these experiments demonstrate that the chickens' age only partially influences resistance to A. galli infection.     

Age-related differences of Ascaridia galli egg output and worm burden in chickens following a single dose infection

Ninety white chickens (Lohmann LSL) were reared under helminth-free conditions and divided into five groups. Four groups were artificially infected with 250 embryonated Ascaridia galli eggs at the age of 6, 12, 18 or 24 weeks. Ten birds were kept as uninfected controls. Six and 10 weeks after infection (p.i.), individual faecal egg counts (FEC) were performed. The birds were slaughtered after the second sampling and their gastrointestinal tracts were examined for the presence of adult A. galli. The FEC increased from the first to the second sampling significantly in all the infected groups. The highest increase was shown in the group infected at 12 weeks of age, whereas the increase in the other groups was relatively moderate. However, the total worm burden and mean FEC at the second sampling were highest (p<0.01) in those birds infected at an age of 12 or 18 weeks. The serum protein and triiodothyronine (T3) levels did not differ significantly (p>0.05) between any of the groups. Thyroxine (T4) was significantly different between the groups infected at 6 and 18 weeks of age (p<0.05), and those at 6 and 24 weeks of age (p<0.01). The thyroid hormone levels correlated significantly with the FEC. Age does not seem to play a major role in resistance to A. galli infections in layers, whereas a bird's hormonal and immune status, related to laying activity, seems to have a significant negative impact on resistance.     

Comparative efficacy of four commercially available heartworm preventive products against the MP3 laboratory strain of Dirofilaria immitis

A controlled laboratory study was conducted to evaluate the efficacy of four commercial products administered as a single treatment for the prevention of heartworm disease caused by Dirofilaria immitis in dogs. Forty-four commercially sourced Beagle dogs, 6-7 months of age, were received at the test site (Auburn University, Department of Pathobiology) on Study Day (SD) -72 to begin acclimation. On SD -30, each dog was inoculated subcutaneously with 100 infective, third-stage D. immitis larvae (MP3 strain, TRS Laboratories, Inc., Athens, GA). On SD -1, 40 dogs weighing 18.2-25.3 lbs were ranked by decreasing body weight and randomized to five groups of eight dogs each. On SD 0, the dogs assigned to Group 1 were treated orally with ivermectin/pyrantel pamoate chewable tablets, Group 2 dogs were treated orally with milbemycin oxime flavored tablets, Group 3 dogs were treated with selamectin topical solution, and Group 4 dogs were treated with imidacloprid/moxidectin topical solution. Group 5 dogs remained nontreated. Dosages for dogs in Groups 1-4 were based on the individual body weight of each dog and current labeled dose banding for each commercial product. All dogs were fasted overnight prior to treatment. Food was returned four hours after treatment. Animals were observed for abnormal clinical signs involving eyes, feces, respiration, behavioral attitude, locomotion/musculature, or skin conditions at prescribed intervals immediately after treatment and at twice daily intervals thereafter. On SD 90, whole blood was collected and tested for adult heartworm antigen. On SDs 119/120, the dogs were euthanized and subjected to necropsy examination for recovery of adult D. immitis and/or worm fragments. At necropsy, all 8 dogs in the nontreated group were infected with adult D. immitis (34-70 worms/dog, geometric mean (GM)=51.6 worms/dog). One or more adult D. immitis and/or worm fragments were recovered from 7 of 8 of the dogs each in Groups 1-3 (87.5% were heartworm positive). The respective GM worm burdens/dog for Groups 1-3 was 2.3, 2.4, and 2.3 which resulted in 95.6, 95.4 and 95.5% efficacy, respectively. No worms were recovered from any of the 8 dogs in Group 4 resulting in 100% efficacy.     

Efficacy of a commercially available coryza vaccine against challenge with recent South African NAD-independent isolates of Haemophilus paragallinarum in chickens

In South Africa the incidence of NAD-independent Haemnophilus paragallinarum isolation from clinical cases is increasing. This study was carried out to test whether a commercially available coryza vaccine (Nobilis Coryza, Intervet International BV) could protect chickens against challenge with recent NAD-independent isolates. SPF chickens were vaccinated twice at 3 and 7 weeks of age and were challenged at 9 weeks of age with 5 different NAD-independent isolates of serotype A or C-3. The results after challenge show that the coryza vaccine induces good protection against challenge with the different South African NAD-independent isolates of H. paragallinarum, including serotype C-3.     

Efficacy of ivermectin against experimental and natural infections of Gasterophilus spp in ponies

Antiparasitic efficacy of ivermectin against migrating Gasterophilus intestinalis was evaluated in 36 treated and 24 nontreated (n = 12) or vehicle-treated (n = 12) ponies experimentally and naturally infected with G intestinalis and naturally infected with G nasalis. Each pony was experimentally infected with 500 G intestinalis 1st instars in 2 divided doses on days -14 and -7 before treatment. On day 0, ivermectin was administered at the rate of 200 micrograms/kg of body weight by IV (n = 12) or IM injection (n = 12) or given as an oral paste (n = 12). Ponies were euthanatized and necropsied 21 days after treatment. In each nontreated or vehicle-treated pony, late 1st-, 1st- to 2nd- instar molt, and early 2nd-instars of G intestinalis were found in the mouth, and 2nd- and 3rd instars of G intestinalis and 3rd instars of G nasalis were found in the stomach. Bots were not found in any ivermectin-treated pony and, thus, ivermectin was 100% effective against oral and gastric stages. Adverse reactions were not observed in ponies given ivermectin by IM injection or orally, but 1 pony given the vehicle IV and 1 pony given ivermectin (in the vehicle) IV had an anaphylactic reaction, resulting in death of the ivermectin-treated pony. It was speculated that the adverse reaction was caused by histamines released in response to vehicle components given by IV injection.     

Comparative efficacy of flubendazole chewable tablets and a tablet combination of febantel, pyrantel embonate and praziquantel against Trichuris vulpis in experimentally infected dogs

Fourteen of 23 dogs developing patent Trichuris vulpis infections by 120 days p.i. with 5000 embryonated eggs were allocated into three groups. One group was treated with flubendazole 220 mg chewable tablets (Flubenol) at the recommended dose regimen once daily for 3 days. The second group was given the recommended single treatment with a tablet containing 150 mg febantel, 144 mg pyrantel embonate and 50 mg praziquantel in combination (Drontal Plus). The third group remained untreated. All dogs were necropsied for worm counts 10 or 11 days after (first) treatment. No worms were recovered from the flubendazole treated dogs resulting in a significant worm count reduction of 100%. In contrast, 2 of 5 animals treated with the combination of febantel, pyrantel embonate and praziquantel remained infected; the geometric mean worm burden was reduced by 99.4% as compared to the control group but did not differ significantly from those of the controls.     

Effects of a herbal complex against Eimeria tenella infection in chickens

A liquid and a powder made from a herbal complex consisting of Uncariae Ramulus cum Uncis, Agrimoniae Herba, Sanguisorbae Radix, Eclipta Prostrate Herba, Pulsatillae Radix, Sophorae Flavescentis Radix, Rehmanniae Radix and Glycyrrhizae Radix were studied for their anticoccidial activities in chickens. Chickens were administered with herbal liquid, powder, diclazuril or without medication during the study and challenged with oocysts of Eimeria tenella. Results indicated that the birds medicated showed less bloody faeces than those without medication. The intestinal lesion was mild in the chicks medicated with herbal liquid without significantly different lesion score when compared with uninfected chicks. The birds with medication had significantly higher body weight gains than birds without medication. Therefore, the herbal complex used in this study was effective against E. tenella infection in chickens.