Introduction
Foot and mouth disease (FMD) is an acute and highly contagious viral disease of all cloven-footed ruminants and pigs. It is an endemic disease in Nigeria and is responsible for devastating economic losses [1]. It can be transmitted via several routes which include oral mucosa, aerosol, and damaged epithelium [2].
The first recorded description of the disease is allegedly reported to be from Northern Italy in 1514 by Hieronymus Fracastorius [3]. In Nigeria, there are no records of pre-colonial existence. The first documented report of FMD in Nigeria was in 1924, with serotype O variant of the FMD virus that was introduced by cattle from the Mambilla Plateau of Cameroon [4]. There are four serotype variants that are currently known to be in circulation in Nigeria. These serotypes include SAT1, SAT2, O, and A [5]. The main reasons for the prevalence of FMD in Nigeria include the uncontrolled movement of cattle herds from one region to another and across borders in search of pastures and water. Additionally, conflicts between cattle herders and farm owners, contact with wild animals such as buffaloes (which may be a source of the virus), and other factors contribute to the spread of the disease [6]. Global estimates place the annual cost of production losses and vaccination practices in FMD-endemic areas between 6.5 and 21 billion US dollars.
In Nigeria, FMD is one of the major hindrances to the growth of animal husbandry. Despite insufficient data and poor investigation of the annual losses due to FMD in cattle production, it has however been estimated that about 7,393,979.04 naira per annum losses in cattle production in Nigeria were attributed to FMD [7]. Due to the endemicity of this viral condition and its great deleterious socio-economic consequences, it is therefore becoming highly imperative for clinicians to develop an appropriate management protocol for the disease. Hence, hematological and biochemical analyses have proved to be vital diagnostic tools for the assessment of the degree and extent of pathological processes in animals in general [8,9]. Variations in the various populations of blood cells such as Lymphocyte and eosinophil can reveal the characteristics of an ongoing infectious process.
Serum chemistry is another very useful prognostic, diagnostic, and therapeutic assessment tool [10]. More often than not, deleterious changes in electrolyte levels, hormone levels, glucose, cholesterol, amino acids, and so on, are usually responsible for the death of sick animals [11]. Moreso these changes in blood and serum parameters have been extensively analyzed in most endemic diseases of cattle.
Despite the importance and prevalence of FMD in Nigeria, and its negative impact on the economy and the livelihoods of cattle farmers year after year, little or nothing is known about the clinical, hematological, and biochemical parameters in FMD-infected and non-infected Nigerian cattle. Furthermore, these parameters have not been compared previously.
In this study, the clinical, hematological, and biochemical parameters in FMD-infected and non-infected Nigerian cattle are compared, along with differences in FMD susceptibility among indigenous cattle breeds, sexes, and ages.
Materials and Methods
Ethical statement
Sampling and laboratory analyses were conducted following the University of Ibadan’s Research Ethics Committee (ACUREC) guidelines in Ibadan, Nigeria.
Study locations
The samples were collected between June and September 2022 from two locations in Ibadan City: Akufo Farm Settlement and Ibadan Central Abattoir, Oyo State. In the Akufo farm settlement, FMD-infected cattle were sampled during an outbreak of FMD that occurred in July 2022 in the Akufo farm settlement. Non-infected cattle were sampled on the slaughter slab in the Ibadan Central Abattoir, Amosun, and Akinyele local government areas of Oyo State. The climatic conditions in the two locations were similar, with a high rainfall pattern (1,200–1,350 mm per year), temperatures varying between 27°C and 32°C, and relative humidity ranging from 70% to 90%. The vegetation pattern is typically that of a rainforest [12] (Fig. 1).
Studied animals
The animals were divided according to their apparent characteristics into males, females, young adults, and adults. They were also divided according to clinical signs and FMD rapid diagnostic kit confirmation into infected and uninfected [13,14]. The pathognomonic signs of FMDV infection considered includes; excessive salivation, high temperature, oral and nasal mucosa vesicles and blisters, vesicles and blisters on the coronary band, and the inter-digital space of the feet.
Rapid diagnostic kit procedure
Herdscreen ®FMD NSP Antibody Rapid test kit was used for the confirmatory diagnosis of FMD in the sampled animals. The test kits work on a principle of immunohistochemistry and capture the antibody developed during the course of the infection. The following highlights the procedure for the test; the test cassette was removed from the foil pouch, and placed on a horizontal surface, and 10 μl of whole blood was collected via venipuncture and added to a well labeled “S” using a dropper provided in the kit. Afterward, time was given for the absorption of the whole blood into the well, two drops of the diluent were added, and the entire set-up was observed for 10 minutes, after which the result was read.
Figure 1.
Akufo farm settlement, Ibadan and Central Abattoir, Akinyele, Ibadan.
Figure 2.
FMD rapid diagnostic kit.
The result was interpreted by the appearance or absence of a colored line on the “C” or “T” band of the test cassette. A color line on the “C” band only indicates the absence of FMD antibodies in the blood sample. Color lines on the “C” and “T” bands of the test cassette read positive for the presence of the antibodies to FMD, and a single-colored line on the “T” band gives an invalid test result [15] (Fig. 2).
Hematological and biochemical analyses
The hematological parameters were analyzed using standard methods such as microhematocrit, cyanomethemoglobin, hemocytometer, and others as previously adopted by [9,16]. Biochemical parameters such as total protein, albumin, globulin, glucose, cholesterol, triglycerides, creatinine, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, sodium, and potassium were analyzed using commercial test kits supplied by Fortress Diagnostics Limited (UK) as previously described by [14,16,17]
Statistical analyses
The collected data were summarized using descriptive statistics to establish frequencies and percentages and presented in tables. Student’s T-test was employed to compare the Mean ± SD of FMD-infected and non-infected cattle. All statistical tests were conducted using the statistical package for social sciences (SPSS) version 26 (SPSS Inc., Chicago).
Results
Table 1 revealed the table of abbreviations and their full meaning and interpretation.
The percentage of FMD infected and non-infected Sokoto Gudali sampled were 50% and 50%, respectively, Red Bororo sampled were 20% and 80%, White Fulani sampled were 55.6% and 44.4%, and Crossbreed sampled were 16.7% and 83.3%, respectively.
The percentage of FMD-infected and non-infected cattle regarding sex indicates 31.6% infected and 68.4% non-infected among cow, respectively, whereas bull shows 36.4% infected and 63.6% non-infected, respectively. FMD occurrence among different age groups revealed 28.6% infected and 71.4% non-infected among young cattle, respectively, while older cattle show 37.5% infected and 62.5% non-infected, respectively (Table 2).
There was a significant difference with higher Mean ± SD values of heart rate, pulse rate, and respiratory rate with p-values of 0.018, 0.023, and 0.048, respectively, in FMD-infected cattle when compared with the values in non-infected cattle (Table 3).
However, all erythrocytic parameters were within the normal reference range. There were significant reductions in the values of Mean ± SD of PCV, HB, MCV, and MCH in FMD-infected cattle compared to non-infected cattle with p-values of 0.016, 0.015, 0.010, 0.001, and 0.001, respectively. However, most leucocytic indices were within the reference range. There were significant differences in the Mean ± SD of lymphocytes, absolute lymphocytes, and platelets with lower values of 35.00 ± 4.52, 2.16 ± 0.33, and 8.00 ± 0.00 in infected cattle compared to 71.60 ± 4.78, 4.72 ± 1.10, and 9.20 ± 1.01 in non-infected cattle, respectively. Significant differences were also observed in the values of neutrophils, and absolute neutrophils with higher values of 63.90 ± 4.43, and 3.93 ± 0.34 in an infected group compared to 27.15 ± 4.80, and 1.76 ± 0.40 in the non-infected group (Table 4).
Table 1.
Abbreviation table.
| Serial number | Abbreviation | Full meaning |
|---|---|---|
| 1 | FMD | Foot and mouth disease |
| 2 | PCV | Packed cells volume |
| 3 | HB | Haemoglobin |
| 4 | RBC | Red blood cell |
| 5 | MCH | Mean corpuscular hemoglobin |
| 6 | MCV | Mean corpuscular volume |
| 7 | MCHC | Mean corpuscular haemoglobin concentration |
| 8 | AST | Aspartate aminotransferase |
| 9 | ALT | Alanine aminotransferase |
| 10 | ALP | Alkaline phosphatase |
| 11 | Na+ | Sodium |
| 12 | K- | Potassium |
Table 2.
Breed, sex, and age distribution of cattle sampled and their percentage of occurrence.
| Parameters | Number of infected / % 20/33.3 |
Number of non-infected / % 40/66.7 |
Total / (%) 60/100 |
|---|---|---|---|
| Breeds | |||
| Sokoto Gudali | 4/50 | 4/50 | 8/100 |
| Red Bororo | 2/20 | 8/80 | 10/100 |
| White Fulani | 10/55.6 | 8/44.4 | 18/100 |
| Cross | 4/16.7 | 20/83.3 | 24/100 |
| Sex | |||
| Male | 8/36.4 | 14/63.6 | 22/100 |
| Female | 12/31.6 | 26/68.4 | 38/100 |
| Age | |||
| Young | 8/28.6 | 20/71.4 | 28/100 |
| Adult | 12/37.5 | 20/62.5 | 32/100 |
Table 3.
Clinical parameters of the FMD-infected and non-infected Cattle (Mean±SD).
| Clinical parameters | Infected group n=20 | Range | Non-infected group n=40 | Range | p-values | Reference values |
|---|---|---|---|---|---|---|
| Temperature (oC) | 40.5 ± 0.38 | 32.5–48.0 | 38.9 ± 0.54 | 30.7–46.1 | 0.076 | 36.7–39.1 |
| Heart rate (beats/minute) | 86.2 ± 0.62 | 78.8–94.0 | 72.4 ± 0.37 | 64.0–80.4 | 0.018* | 48–84 |
| Pulse rate (beats/minute) | 90.5 ± 0.98 | 82.0–98.9 | 78.2 ± 0.34 | 70.1–86.2 | 0.023* | - |
| Respiratory rate (breaths/minute) | 44.5 ± 0.19 | 38.6–52.7 | 36.8 ± 0.73 | 30.9–42.2 | 0.048* | 26–50 |
| Statistical significance between the infected group and infected group; *p < 0.05. | ||||||
Table 4.
Hematological parameters of the FMD-infected and non-infected cattle (Mean±SD).
| Erythrocytic Parameter | Infected group n=20 | Range | Non-infected group n=40 | Range | p-values | Reference values |
|---|---|---|---|---|---|---|
| PCV (%) | 24.5 ± 3.34 | 18.90–36.00 | 30.0 ± 6.32 | 20.0–39.00 | 0.016* | 24–46 |
| Hb conc. (gm%) | 8.01 ± 1.11 | 6.20–9.50 | 9.87 ± 2.11 | 6.50–12.90 | 0.015* | 8–15 |
| RBC count(x1012/l) | 9.30 ± 1.22 | 7.04–10.63 | 7.27 ± 2.14 | 4.24–11.41 | 0.010* | 5–10 |
| MCV (fl) | 26.83 ± 5.28 | 17.87–36.75 | 42.82 ± 8.66 | 27.63–62.17 | 0.001* | 40–60 |
| MCH (pg) | 7.80 ± 2.87 | 1.06–12.07 | 14.07 ± 2.86 | 9.07–20.43 | 0.001* | 11–17 |
| MCHC (g/dl) | 32.69 ± 0.87 | 32.61–32.86 | 32.83 ± 0.21 | 32.29–33.08 | 0.045 | 30–36 |
| WBC (x109/l) | 6.16 ± 0.39 | 5.60–6.80 | 6.56 ± 1.35 | 4.04–9.20 | 0.370 | Not available |
| Lymphocyte (x109/l) | 35.00 ± 4.52 | 30.00–42.00 | 71.60 ± 4.78 | 64.00–78.00 | <0.001* | 62–63 |
| Neutrophil (x109/l) | 63.90 ± 4.43 | 57.00–68.00 | 27.15 ± 4.80 | 20.00–35.00 | <0.001* | 15–33 |
| Monocyte (x109/l) | 1.40 ± 0.52 | 1.00–2.00 | 1.25 ± 0.44 | 1.00–2.00 | 0.416 | Not available |
| Absolute lymphocyte (x109/l) | 2.16 ± 0.33 | 1.68–2.62 | 4.72 ± 1.10 | 2.99–6.90 | <0.001* | Not available |
| Absolute monocyte (x109/l) | 0.84 ± 0.29 | 0.06–0.13 | 0.08 ± 0.34 | 0.05–0.18 | 1.000* | Not available |
| Absolute neutrophil (x109/l) | 3.93 ± 0.34 | 3.42–4.42 | 1.76 ± 0.40 | 1.10–2.46 | <0.001* | Not available |
| Platelet (x109/l) | 8.00 ± 0.00 | 8.00–8.00 | 9.20 ± 1.01 | 8.00–10.00 | 0.001* | 10–80 |
Statistical significance between the infected group and infected group; *p < 0.05.
The biochemical parameters of the FMD-infected and non-infected cattle reveal diverse variations. Significant differences were observed in the value of most of the biochemical parameters. The Mean ± SD values of total protein, albumin, globulin, glucose, creatinine, AST, ALT, ALP, Na+, and K- were significantly lower in the FMD-infected group compared to the non-infected group. The values were 2.69 ± 0.42, 1.03 ± 0.39, 1.66 ± 0.39, 49.00 ± 5.68, 1.22 ± 0.20, 28.10 ± 5.36, 19.10 ± 6.44, 24.60 ± 5.36, 37.90 ± 6.19, and 30.20 ± 9.32 in FMD infected cattle compared to 3.49 ± 0.86, 1.23 ± 0.16, 2.28 ± 0.79, 64.56 ± 12.31, 1.62 ± 0.46, 44.20 ± 9.29, 34.35 ± 8.01, 38.10 ± 8.63, 54.55 ± 9.97, and 46.00 ± 9.36 in non-infected cattle, respectively (Table 5).
Table 5.
Biochemical parameters of the FMD-infected and non-infected cattle (Mean ± SD).
| Biochemical parameter | Infected group n=20 | Range | Non-infected group n=40 | Range | p-values | Reference value |
|---|---|---|---|---|---|---|
| Total serum protein (g/dl) | 2.69 ± 0.42 | 2.12–3.21 | 3.49 ± 0.86 | 2.24–4.80 | 0.009* | 6.7–7.5 |
| Albumin(g/dl) | 1.03 ± 0.39 | 1.00–1.10 | 1.23 ± 0.16 | 1.04–1.60 | 0.001* | 2.5–3.8 |
| Globulin(g/dl) | 1.66 ± 0.39 | 1.00–1.10 | 2.28 ± 0.79 | 1.14–3.50 | 0.026* | 3.0–3.5 |
| Glucose (mg/dl) | 49.00 ± 5.68 | 42.00–58.00 | 64.56 ± 12.31 | 34.00–84.00 | 0.001* | 40–100 |
| Cholesterol (mg/dl) | 26.80 ± 3.46 | 20.00–32.00 | 28.40 ± 8.54 | 16.00–45.00 | 0.576 | Not available |
| Triglycerides (mg/dl) | 35.90 ± 5.49 | 26.00–42.00 | 35.35 ± 8.70 | 22.00–52.00 | 0.857 | Not available |
| Creatinine (mg/dl) | 1.22 ± 0.20 | 1.00–1.54 | 1.62 ± 0.46 | 1.00–2.22 | 0.014* | 0.5–2.2 |
| AST (mol/l) | 28.10 ± 5.36 | 22.00–36.00 | 44.20 ± 9.29 | 26.00–57.00 | <0.001* | 60–125 |
| ALT (mol/l) | 19.10 ± 6.44 | 10.00–28.00 | 34.35 ± 8.01 | 22.00–48.00 | <0.001* | 4–11 |
| ALP (mol/l) | 24.60 ± 5.36 | 15.00–33.00 | 38.10 ± 8.63 | 24.00–54.00 | <0.001* | 10–77 |
| Na+(mEq/l) | 37.90 ± 6.19 | 30.00–47.00 | 54.55 ± 9.97 | 38.00–70.00 | <0.001* | 136–144 |
| K+(mEq/l) | 30.20 ± 9.32 | 20.00–44.00 | 46.00 ± 9.36 | 34.00–68.00 | <0.001* | 3.6–4.9 |
Statistical significance between the infected group and infected group; *p<0.05.
Discussion
The present work confirms and reports the current endemicity of FMD in Ibadan, Oyo state Nigeria. The persistent enzootic nature of FMD in Nigerian states may be due to the failure to establish a successful vaccination program, an extensive management system with unrestricted animals’ movement, and ineffective livestock policies. The endemicity of FMD in Nigeria that was confirmed with rapid field diagnostic kits in this present study corroborates the findings of earlier researchers who have also confirmed the presence of FMD in cattle in south-western Nigeria [5,18]. The highest incidence of FMD cases observed in the White Fulani breed compared to other breeds of cattle may probably be due to the large population of the White Fulani breed of cattle in Nigeria in general. Other researchers also reported the highest seroprevalence of FMD in White Fulani (Bunaji) compared to other breeds of cattle in Nigeria. They also alluded to the fact that fewer number of other breeds aside White Fulani was a major factor. This assertion of the white Fulani breed being the majority among the Nigerian cattle population was also supported by the findings of [12,19,20]. A higher incidence of FMD in bulls compared to cows in this present study could be due to age, stress, and hormonal-related factors. Higher susceptibility of male cattle (Bull) to FMD compared to female cattle (Cow) had been previously documented [21]. An earlier report of Bull possessing 2.83 higher chances of been infected with Foot and Mouth disease virus (FMDV) than females have also been reported [22]. However, a high incidence of FMDV in females’ cattle in Northwest Ethiopia compared to males have been reported by [23]. The differences observed may be due to differences associated with locations, breeds, and climatic factors.
Furthermore, a greater percentage of FMD cases were recorded in the adults, than in the young according to this study. This could be due to the presence of maternal antibodies against different serotypes of the FMDV in the young. This could also be due to the fact that there are fewer activities and relatively reduced external contacts in young cattle than in adults; which may often roam around for other mates or in search of feed, be transported to markets for sales, and so on. This finding is supported by an earlier study that stated that adults are more susceptible to FMD than young cattle less than 2 years old because they tend to have higher concentrations of circulating antibodies to FMDV [24]. This also agrees with the previous observation of two researchers in their studies, where they reported that adult cattle were more susceptible to FMD than younger ones in the Comilla and Magura regions of Bangladesh, respectively, both stating malnutrition, weaker immune system, and poor management practices as the primary causes [25,26]. All the erythrocytic parameters among FMD-infected cattle were lower, except RBC compared to non-infected cattle. This could be associated with the hemorrhages from the vesicles, blisters, and ulcerations in the foot, buccal cavity, teats, and lips of infected cattle always associated with FMD infection. This may also be due to reduced appetite associated with pain due to FMD lesions in the mouth of the affected animals. However, the higher RBC values observed in FMD-infected cattle compared to non-infected cattle could possibly be due to relative polycythemia, that often caused by loss of body fluids, such as dehydration, chronic pain, and stress. Oral lesions make feeding and drinking difficult for cattle. Hence, dehydration could result from a sustained inability to consume enough water. This causes a reduced plasma volume, which gives a relatively higher concentration of red blood cells during cell counts [27]. This disagrees with an earlier study that stated that the MCV in the infected group was higher in comparison with the non-infected group, and a significantly lower RBC count in the infected group than in the uninfected group. He attributed these hematological changes to the possible involvement of endocrinopathies in FMD in cattle [28].
The leucogram picture was also quite noteworthy. The lymphocyte counts for the infected group were lower than that of the non-infected groups. This pronounced decrease in the lymphocytic population can be explained by the immunosuppression that is characteristic of FMDV infection. It is an established fact in the literatures that the FMD virus prevents the activation of Toll-like receptor pathways in dendritic cells present in tissues of the cattle’s body [29]. Hence, suppressing the phagocytic and antigen-presenting roles of these cells, which may probably explain why there was significant lymphopenia in the infected group. This finding of FMDV infection being associated with immunosuppression is consistent with the previous findings of other researchers who observed that lymphopenia is associated with FMDV infection [30]. The neutrophilia observed in FMD-infected cattle compared to uninfected cattle may be due to secondary bacterial complications due to the immunosuppressive effects of FMDV infection, especially in ill-managed herds.
The observable hypoproteinemia and hypoalbuminemia observed in this present study can be associated with the poor feed consumption that results due to the oral lesions which make feeding difficult. Malnutrition is a major cause of hypoproteinemia [31]. Also, the negative acute phase feature of albumin causes a decrease in its concentration in the serum during inflammatory processes. This decrease in the total serum protein levels in naturally infected FMD cattle is consistent with the findings of [32,33] who also recorded lower serum protein concentrations in their study of the serum biochemical changes associated with FMD infection. However, these results do not agree with the findings of [30] who recorded no significant change in the serum levels of the total protein, albumin, and globulin of infected FMD cases in cattle in India. These contrasts may probably be associated with differences in the genetic character of the selected breed of cattle, environmental factors, and other peculiar experimental conditions of the research.
The hypoglycemia recorded in FMD-infected cattle in comparison with uninfected cattle can be attributed to reduced feed intake associated with the oral lesions in FMD. This finding is however in contradiction with the finding of a study that observed higher levels of glucose in the infected groups than in the uninfected group [28]. He explained that this increase was due to insulin secretion interference due to FMD-associated hypocalcemia. The lower serum creatinine levels in the infected cattle compared to the uninfected cattle could also be a result of malnutrition-associated FMDV infection. This finding disagrees with the findings of [28,33] who indicated that there was a significant increase in the levels of serum creatinine in cases of FMD. Possible focal degeneration of muscles which results from lesions in the coronary bands of the hooves, teats, buccal cavity, and lips in FMD were part of the reasons stated as probable causes. The alteration was observed as a decrease in the values of liver enzymes seen in FMDV-infected cattle compared to non-infected cattle. This indicates that FMD does not necessarily cause damage to internal organ structures such as the liver, kidney, pancreas, muscles, bones, and so on. This result is also corroborated by an earlier study that stated that there were no internal organ damaging effects associated with foot-and-mouth-disease viral infection of [30]. This study is in tandem with the earlier observation of lower values of 41.53 ± 12.4 and 97.30 ± 42.8 of ALT and AST, respectively, in the FMD-infected group, as opposed to higher values of 54.60 ± 19.40 and 99.90 ± 25.30 of ALT and AST, respectively, in the non-infected group. Thus, suggesting that FMD does not cause damage to internal organs of the body [28]. But, this study is, however, not in conformity with the observation of a study that liver function was affected by the FMD viral infection in cattle [1,33].
Conclusion
The study therefore concluded that White Fulani breeds of cattle were the most susceptible breed and cross-bred cattle were the least in terms of susceptibility. Bulls were found to be more susceptible compared to cows while adult seems more susceptible to FMD in comparison to young cattle. Significant variations in the hematological and serum biochemical parameters between FMD-infected and non-infected indigenous breeds of cattle in Nigeria were observed, with the infected group revealing lower erythrocytic parameters compared to the non-infected group. Generalized neutrophilia, lymphopenia, hypoproteinemia, hypoalbuminemia, hyperglobulinemia, hypoglycemia, hypocreatinemia, lower AST levels, lower ALT levels, lower ALP levels, and lower Na+ and K+ levels were also observed in FMD infected group compared to non-infected cattle.
Recommendation
Generalized neutrophilia, lymphopenia, hypoproteinemia, hypoalbuminemia, hyperglobulinemia, hypoglycemia, hypocreatinemia, reduction in the values of liver and muscle enzymes, and lower Na+ and K+ values should be considered in the designing of treatment and management protocol for FMD in cattle. Endemicity of FMD in southwest Nigeria is real and current and more strategic approaches should be formulated by the stakeholders to mitigate against the deleterious effect of the condition. More research should be done to establish the current strain of the virus circulating in Nigeria’s cattle population with the aim of developing an appropriate vaccine for the disease.
Authors contributions
Conceptualization, S.C.O, P.S.A, E.A.A, O.A.; methodology, S.C.O, A.A.A.; formal analysis, S.C.O, E.A.A; writing—original draft preparation, S.C.O; writing—review and editing, S.C.O, P.S.A, E.A.A, O.A, A.A.A; all authors have read and agreed to the published version of the manuscript.
Acknowledgments
The authors acknowledge Mr Abubakar and Abdulahi, the animal handlers at the Akufo farm settlement for their assistance and support during sampling. The authors are immensely grateful to Mrs Adetiba of the General Laboratory Department of Veterinary Medicine, University of Ibadan, for her laboratory support.
Declaration of interest
The authors declare no conflicts of interest in relation to the publication of this manuscript.
