Introduction
There are many varieties of poultry reared in Nigeria among which are domestic pigeons (Columba livi domestica) which have been classified as mini-livestock [1–2] and have been considered a rapid means of obtaining animal protein.
Domestic pigeons (Columba livia domestica) are among the poultry species kept in Makurdi, Benue State, Nigeria, where they are commonly seen daily scavenging for food together with other poultry species. They are used mainly as a source of protein for human consumption [3]. However, poor husbandry systems and diseases especially parasitic infestations cause great losses in this sector. Pigeons may be infected with many organisms thereby serving as a reservoir of many parasitic diseases for poultry and the close contact of pigeons with other domestic birds increases the risk of parasitic infestation in these birds [4].
Several health problems can affect pigeons but parasite infections play a major role. They constitute a major source of infection and transmission of diseases [5]. This is because domestic pigeons are reared extensively and feed on a wide range of food items including grains, slugs, earthworms, and insects that in many instances may carry infective stages of intestinal parasites [6].
Various parasites including Helminths invade the gastrointestinal tract of pigeons affecting their growth, development, and productivity and at times, resulting in death [7].
Helminth parasites of poultry are generally cestodes, nematodes, and trematodes of which the nematodes are regarded as the most important group considering both the number of species and the harm they cause [8]. Only a few numbers of cestodes and trematodes are known to parasitize poultry [9–10].
Thus, this study was conducted to determine the prevalence of gastrointestinal helminth parasites of domestic pigeons and investigate the differences in pathological markers such as hematology, serum biochemistry, and gross and histopathology between the infected and non-infected birds in Makurdi, Benue State, Nigeria.
Information obtained from this study will help in contemplating measures to improve the health of pigeons as well as those of other contact poultry species. This will increase the availability of animal protein thereby combating malnutrition among the poor rural dwellers.
Materials and Method
Study area
The study was conducted in Makurdi, the Capital of Benue State located in the North Central Zone of Nigeria. Benue State has an estimated total poultry population of 6,735,041 [11]. Makurdi is located in the North Eastern part of Benue State. It is located within the flood plain of the lower River Benue valley.
Study population and sample size calculation
This consisted of domestic pigeons which had owners who provided housing for them to return to at night and fed them with grains (mainly guinea corn) and water in the morning before they flew away and scavenged for themselves the rest of the day. No specific preference was given to age, sex, breed, health status, and management system during sampling.
The sample size was calculated based on the prevalence rate of intestinal helminth parasites of pigeons reported by Mohammed et al. [12] from Kano, Nigeria, as 27.97% using the formula of Thrusfield [13];
where n is the sample size, Z is the statistic corresponding to the level of confidence (95% or 1.96), p is expected prevalence (27.97%), and d is precision (5% or 0.05).
N=310 samples.
A total of 310 pigeons (Columba livia domestica) were, therefore, purchased from local farmers within Makurdi, Benue State, Nigeria, from the months of January, 2020 to November, 2020. They were caught at night, kept in cages, and transported the following morning to the Veterinary Teaching Hospital, Joseph Sarwuan Tarka University, Makurdi.
Hematology and serum biochemistry
One milliliter of blood was collected from each pigeon by venipuncture of the jugular vein into a labeled sample bottle containing 1 mg of ethylene diamine tetra acetic acid anticoagulant. All hematological determinations followed standard procedures and were done immediately upon collection of blood samples. Packed cell volume (PCV) was determined by the microhematocrit method [14], while hemoglobin concentration (HbC) was determined by the cyanomethemoglobin method [15]. Red blood cell (RBC) and total white blood cell (WBC) counts were done by the hemocytometer method using Natt and Herrick’s solution as the diluting fluid [16]. The smears for differential leukocyte count were prepared and stained by the Giemsa technique and enumerated by the battlement counting method [14]. The mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) were calculated using the standard formulae [17–18].
Blood for serum biochemical procedures was collected into plain bottles and allowed to coagulate for 1 hour before centrifuging at 3,500 rpm for 5 minutes using a centrifuge. The serum was then separated and the total protein was measured using the Biuret method according to Duncan et al. [19] and albumin levels were determined chronologically using Randox. The globulin fraction was calculated by subtracting the albumin fraction from the total protein.
Simple flotation technique for detection of parasite eggs
Fecal samples were collected into sterile polythene bags using gloved hands, identified appropriately, and taken immediately to the laboratory for analysis. Analysis was carried out within 3 hours of collection to identify nematode and cestode eggs using the flotation technique [20]. The eggs were identified using a guide by Thienpont [21]. Saturated salt solution was used as the flotation medium and helminth eggs present were viewed under the microscope at 10X objective and confirmed at 40X objective.
Examination of gastrointestinal tract (GIT) for parasite detection
The gastrointestinal tract of infected pigeons was removed at necropsy and cut open longitudinally to expose the lumen [22]. Helminths seen were isolated and preserved in a specimen bottle containing 70% alcohol before identification.
Helminths were processed according to procedures outlined by Gibbons et al. [23] and identified using the helminthological keys of Soulsby [24], Permin and Hansen [25], and Norton and Ruff [26]. Intestinal tissue samples were collected and preserved in 10% buffered formalin and processed for histopathological examination according to the procedure of Drury and Wellington. [27].
Data analysis
Data collected from this study were represented based on the positivity or negativity of parasitic infection among the pigeon population sampled.
Data collected from the study were analyzed using Graph pad PrismR software version 5.0 (USA) and presented as means and standard deviations (S.E.M ± S.D). Values of p < 0.05 were considered significant. The unpaired Student-t test was used to compare pathological markers between infected and uninfected samples.
The prevalence of gastrointestinal helminths was calculated and expressed in percentages.
Results
A total of 310 pigeons were sampled and the prevalence of gastrointestinal parasites of pigeons in Makurdi was 88.7% (275/310) composed of different species of cestodes and nematodes.
Table 1.
Helminth parasites identified from domestic pigeons in Makurdi, Benue State, Nigeria.
| Helminths | Number positive | Prevalence (%) | |
|---|---|---|---|
| Cestodes | Raillietina echinobothrida | 135/310 | 43.5 |
| Raillietina tetragona | 84/310 | 27.1 | |
| Raillietina cesticillus | 20/310 | 6.4 | |
| Amoebotaenia cuneate | 12/310 | 3.9 | |
| C. infundibulum | 8/310 | 2.6 | |
| H. cantaniana | 18/310 | 5.8 | |
| C. proglottina | 14/310 | 4.5 | |
| Nematodes | A. columbae | 39/310 | 12.6 |
| H. gallinarum | 15/310 | 4.8 | |
| C. columbae | 2/310 | 0.6 | |
| S. brumpti | 3/310 | 1 | |
| H. gallinarum | 2/310 | 0.6 | |
| A. anseris | 1/310 | 0.3 | |
| Total | 275 | 100 | |
Table 2.
Overall hematological parameters of pigeons infected with gastrointestinal parasites within Makurdi metropolis, Benue State, Nigeria.
| Parameter | Gastrointestinal parasites | |
|---|---|---|
| Infected | Non-infected | |
| Packed cell volume (%) | 45.04 ± 5.84a | 45.26 ± 4.91a |
| Haemoglobin concentration (g/dl) | 14.91 ± 2.00a | 15.09 ± 1.63a |
| RBC (× 1012/l) | 2.75 ± 0.95a | 2.93 ± 0.97a |
| MCV (fl) | 185.2 ± 74.05a | 168.4 ± 48.34a |
| MCH (pg) | 61.14 ± 23.72a | 56.04 ± 16.15a |
| MCHC (g/dl) | 33.67 ± 6.50a | 33.50 ± 3.35a |
| Total leukocyte count (× 109/l) | 26.91 ± 5.50a | 23.57 ± 4.11b |
| Heterophil count (× 109/l) | 12.59 ± 3.55a | 7.17 ± 2.05b |
| Lymphocyte count (× 109/l) | 12.16 ± 3.39a | 14.52 ± 3.08b |
| Monocyte count (× 109/l) | 0.79 ± 0.60a | 0.21 ± 0.25b |
| Eosinophil count (× 109/l) | 1.36 ± 0.70a | 0.18 ± 0.25b |
Values with different superscript alphabet along the same row differ significantly (p < 0.05).
Among the parasites identified, Raillietina was the genus with the highest prevalence of 67.4% (209/310). In this genus, Raillietina echinobothrida had the highest prevalence of 43.5% (135/310) then Raillietina tetragona at 27.1% (84/310), and finally, Raillietina cesticillus with a prevalence of 6.4% (20/310).
Other species include; Ascaridia columbae 12.6% (39/310), Hymenolepis cantaniana 5.8% (18/310), Heterakis gallinarum 4.8% (15/310), Cotugnia proglottina 4.5% (14/310), Amoebotaenia cuneata 3.9% (12/310), Choataenia infundibulum 2.6% (8/310), Subulura brumpti 1% (3/310), Capillaria columbae 0.6% (2/310), Hartertia gallinarum 0.6% (2/310), and the lowest prevalence; Amidostomum anseris 0.3% (1/310).
Cestodes (Tapeworms) included; R. echinobothrida, R. tetragona, R. cesticillus A. cuneata, C. infundibulum, H. cantaniana, and C. proglottina and Nematodes included; A. columbae, H. gallinarum, C. columbae, S. brumpti, H. gallinarum, and A. anseris (Table 1).
Hematological changes
The overall mean (± SD) PCV, HbC, total count RBC, MCV, MCH, and MCHC showed no significant (p > 0.05) differences between non-infected and helminth parasite infected pigeons. There was also no significant (p > 0.05) difference in the overall mean (± SD) lymphocyte counts between pigeons infected with helminth parasite and non-infected pigeons (Table 2).
Table 3.
Overall serum protein parameters of pigeons infected with gastrointestinal parasites within Makurdi metropolis, Benue State, Nigeria.
| Parameter | Gastrointestinal parasite | |
|---|---|---|
| Infected | Non-infected | |
| Total protein concentration (g/dL) | 2.93 ± 1.32a | 3.62 ± 1.32b |
| Albumin concentration (g/dL) | 1.17 ± 0.41a | 1.20 ± 0.34a |
| Globulin concentration (g/dL) | 1.76 ± 1.26a | 2.43 ± 1.26a |
Values with different superscript alphabet along the same row differ significantly (p < 0.05).
The overall mean (± SD) total leucocyte count was significantly (p < 0.05) higher in parasite-infected (26.91 ± 5.50 × 109/l) pigeons compared to non-infected pigeons (23.57 ± 4.11 × 109/l). There were significantly (p < 0.05) higher overall mean (± SD) heterophil count in helminth parasite-infected (12.59 ± 3.55 × 109/l) pigeons compared to non-infected pigeons (7.17 ± 2.05 × 109/l). The overall mean monocyte counts in helminth parasite-infected (0.79 ± 0.60 × 109/l) pigeons and non-infected pigeons (0.21 ± 0.25 × 109/l) were higher (p < 0.05). Similarly, the overall mean eosinophil counts in GIT parasite-infected (1.36 ± 0.70 × 109/l) pigeons were significantly (p < 0.05) higher than in non-infected pigeons (0.18 ± 0.25 × 109/l).
Serum biochemical parameters
The overall mean (±SD) total protein concentrations, serum albumin, and globulin levels are presented in Table 3.
There were significantly (p < 0.05) lower overall total protein and globulin concentrations in helminth parasite-infected (2.93 ± 1.32 g/dl) (1.76 ± 1.26 g/dl) pigeons than in non-infected pigeons (3.62 ± 1.32 g/dl) (2.43 ± 1.26 g/dl).
There were no significant (p > 0.05) differences in overall mean albumin concentrations between helminth parasite-infected and non-infected pigeons.
Plate 1.
Photograph of the small intestine of domestic pigeons showing; a) Tape worms (arrows) within the lumen, b) Several round worms (arrows), and c) Nodular masses on the mucosa (pointer) (P) and serosa (arrow).
Plate 2.
Photomicrograph of a section of the small intestine (H and E stain X400) of domestic pigeon showing; a) Necrosis of the villi epithelium (N) and mononuclear inflammatory cells in the lamina propria (arrows), b) Villi atrophy (arrow) and necrosis (N) of the intestinal crypts, c) Sloughing of the villi epithelium (arrow), and d) Marked inflammatory cell in the submucosa extending into the muscularis (arrows).
Gross and histopathology
Helminths (both cestodes and nematodes) were identified across various sites within the lumen of the gastrointestinal tract (plate 1a and plate 1b) with nodular lesions of different sizes seen on both the mucosa and serosa surfaces of the intestine (plate 1c).
Histopathology of the small intestine showed the marked presence of inflammatory cells in the mucosa, submucosa, and even the muscularis mucosa (Plate 2a and 2d). There was also villi atrophy (Plate 2b), necrosis of villi epithelium (Plate 2a), necrosis of intestinal crypts (Plate 2b), and sloughing of the villi epithelium (Plate 2c).
Discussion
Survey
A total of 310 pigeons were surveyed for gastrointestinal helminths during the study period with an overall prevalence of 88.7% (275/310). This is higher than the 46.7% reported in Owerri, Imo State [28]; 48.3% reported in Zaria, Kaduna State [29]; 78.3% in Jalingo Metropolis, Taraba State [30]; 50% in Port Harcourt, Rivers State [31]; 27.7% in Kano State [12], 64.1% in Ilorin, Kwara State [32]; 23% in Katsina State [33]; 68% in Sylhet District, Bangladesh [34]; 72.8% in YSR Kadapa District, Andhra Pradesh [35]; and 55% in Nepal [36]. Differences in geographical location, number of birds sampled, and type of laboratory tests used might be the possible reasons for the disparity in prevalence recorded in this study and those by other researchers.
Among the pigeons infected with gastrointestinal helminths, 11 genera with 13 different species were identified. Raillietina sp, a cestode had the highest prevalence of 67.4%. Among the species of Raillietina, R. echidnobothrida had the highest prevalence of 43.5%. This is an indication of a higher availability of infective stages and intermediate hosts among the reared pigeons [29]. A similar overall high prevalence of cestodes was reported in the North-East zone [37,38], Adang et al. [39] in Zaria (North West), and Atsineka and Banke [40] in Makurdi (Middle belt) of Nigeria. This finding is dissimilar to that of El-Dakhly et al. [41] who reported a prevalence rate of 7.29% of cestodes in Ben—Saif province in Egypt; but considerably lower than 61.62% reported by Umaru et al. [30] in Taraba State (North East), Nigeria. This variation may be a result of differences in geographical locations and accompanying environmental conditions.
The emergence of cestodes is dependent on suitable intermediate hosts (snails, beetles, pill bugs, ants, and earthworms) required for a complete life cycle with pigeons becoming infected by ingesting such intermediate hosts [42]. Most of the cestodes were encountered in the small intestine where the microhabitat favors their survival. The presence of digested nutrients in the small intestine may influence their restriction to this location, thereby causing intestinal obstruction, weight loss, decreased egg production in laying birds, and general poor body condition [24,43]. This could, in turn, lower the income generation and nutritional status of these poor families.
Effects of helminths on hematology and serum protein levels of pigeons
Gastrointestinal helminths have been suggested to induce anemia via interference with iron intake and/or blood-sucking action leading to blood loss from the gastrointestinal tract [44]. The absence of significant differences in packed cell volume, HbC, total RBC count, MCV, MCH, and mean corpuscular HbC between infected and non-infected pigeons in this study suggests subclinical disease in the infected pigeons, thus the absence of anemia [45].
There were higher total leukocyte counts in infected pigeons compared to non-infected pigeons and this was due to higher heterophil, monocyte, and eosinophil counts. Heterophils and macrophages were reported to play a critical role in tissue debris phagocytosis [46–47]. Although these pigeons were exposed to various infectious agents and inflammatory responses due to their flying habits, the higher heterophil and monocyte counts in the naturally infected pigeons might have been exacerbated by the parasites. Also, the helminth infection might have induced a stressful condition in the infected pigeons leading to increased corticosterone levels with consequent higher heterophil and monocyte counts [48–49]. Since the gastrointestinal tract is rich in mast cells, these cells degranulate following tissue destruction leading to histamine release with consequent attraction of eosinophils [50]. Thus the higher eosinophil counts in infected pigeons might have resulted from this mechanism induced by the destruction of the gastrointestinal tract tissues caused by the helminths. The direct attack of the parasites by eosinophils [46] might be another possible reason for the higher eosinophil counts in infected pigeons as observed in this study.
The lower total protein concentration in infected pigeons might be due to protein loss following the blood-sucking action and/or starvation induced by the helminth burden in the gastrointestinal tract [51]. This was accompanied by lower globulin concentration indicating decreased immune status of the infected pigeons.
Gross and microscopic changes
Grossly, live parasites were present in the intestinal lumen and there were also nodular lesions on the mucosal and serosa surfaces of the intestine. These are consistent with those of previous reports [52–54]. Raillietina echinobothrida, also known as the nodular tape worm reported in this study as having the highest prevalence among the parasites has been reported to be the most pathogenic tapeworm among the Raillietina species [42]. Its presence has often been associated with the formation of nodules (nodular worm) in the intestinal wall of infected birds [55]. This is similar to the findings of this study. In this infection, the young forms of the parasite penetrate with their anterior end deeply into the mucosa and sub-mucosa of the duodenum, resulting in the formation of nodules and hyperplasic enteritis at the site of their attachment [56].
Histopathological study showed ulceration and sloughing of the epithelial lining of intestine mucosa, degeneration, necrosis, and atrophy of intestinal villi. Also, there was desquamation of epithelium, destruction of secretary glands, and infiltration of inflammatory cells similar to findings of Abed et al. [53], Belete et al. [54], Saikia et al. [57], and Terfa et al. [58]. These changes may be linked to the migration of the larvae during the tissue phase of the life cycle. Villi atrophy and infiltration of inflammatory cells may be due to the high parasite burden in the small intestine leading to pressure atrophy and malabsorption.
Conclusion
This study showed that the prevalence of gastrointestinal helminth parasites in domestic pigeons in Makurdi, Benue State, was high (88.7%). The genus Raillietina had the highest prevalence of 67.4% and one of its species, Raillietina echidnobothrida had the highest prevalence of 43.5%.
The presence of these parasites caused a significant increase in the total WBC counts, lymphocyte, monocyte, eosinophil, and heterophil counts. They also caused a significant decrease in the serum total protein and globulin levels in the infected pigeons with intestinal tissues also showing pathological changes.
This indicates that domestic pigeons within Makurdi can serve as reservoirs of parasitic diseases of poultry. Therefore, efforts should be made by veterinarians to routinely deworm these birds.
Recommendation
The deployment of deworming techniques as a means of breaking the transmission cycle of these parasites is recommended for proper control of parasitic infections in pigeons. More Studies need to be conducted on other species of birds reared in close contact with pigeons to check the likelihood of cross infection of parasites among the various species.
Pigeon management programs and public education should be implemented to reduce the risk of a pigeon to livestock transmission of pathogenic agents and parasites in the country. This study has paved the way for further extensive studies related to these helminths which may help in the implementation of future preventive and control measures.
