Survey of Snakes Bites among Snake Endemic Communities in North Eastern Nigeria

Abstract

Snake envenomation is increasingly recognized as a serious, worldwide public health concern and a neglected tropical disease of global importance especially in the North Eastern Nigeria. The scarcity of data regarding such snake fauna couple with its ability to inflict immense misery to the poorest of the population justifies the need to identify such snakes and some of the clinical features of snakebite victims in these endemic areas. Both primary and secondary data were collected during the study. Result revealed that 10 venomous snake species were reported in Gombe, Taraba and Bauchi state. The most abundant snake species is the Echis ocellantus (Carpet or saw scaled viper) having the highest frequency of encounter followed by the Bitis arientans (Puff Adder) and Naja nigricolis (Black Spiting Cobra). The Kaltungo General Hospital in Gombe is one of the major treatment centers in the North-Eastern Nigeria. About 2945 Human snakebite cases were reported in the Hospital in the year 2018, the highest snake envenoming were observed in October with 16.1% frequency while January has the least snakebite cases of 1.7%. The burden of snakebite envenoming in the North-Eastern Nigeria is a serious public health challenge which desperately need to be addressed.

1. Introduction

Snake envenomation or exposure to the toxin from snakebite is a common worldwide occurrence and especially greatest in tropical and subtropical regions. It has a devastating impact on human health as well as the economy through treatment expenditure and loss of productivity [1, 2]. The incidence of snakebite is mostly associated with the warm regions where economic activities of the inhabitants are predominantly agriculture [3].

The incidence of snakebite is sometimes under-documented. Chippaux [4] reported that annually the total number of snake-bites might exceed 5 million with snake-bite mortality of 1,25,000 in the world. It has been reported that the highest burden of snakebite incidence is seen in the rural poor communities of tropical countries in South Asia, Southeast Asia, and sub-Saharan Africa with an estimate of over 3,14,000 bites, 7300 deaths and nearly 6000 amputations occurring from snakebites annually in Sub-Saharan Africa [5].

In Nigeria the majority of snake species that are of medical importance belong to three families viz., Viperidae (Vipers and Adder), Elapidae (Cobras and Mambas) and Colubridae (Boomslag) [6]. The saw-scaled or carpet viper (Echis ocellatus), Cobras (Naja spp.) and puff adders (Bitisarietans) have proved to be the most important cause of mortality and morbidity. Specifically, the Echisocellantus is by far the most common cause of morbidity and mortality in North-Eastern Nigeria [6]. Nigeria is known to be home to a lot of diverse snake species especially in the North Eastern part of the Savannah region with 100–150 lethality in hospitals and also overall mortality of 15.6 daily in Kaltungo [7]. Snake bite envenomation survivors live with temporary or permanent disabilities such as amputation, blindness, disfigurement, mutilation and psychological consequence from depression. The exorbitant cost of antivenom and its scarcity is another problem for poor communities. Despite all that, there is a scarcity of data regarding such snake fauna that can inflict such immense misery to the poor section of the population. The few available literatures restrict the species to three main species as of 2001. Treatment option and critical are provided by various workers [8, 9].

2. Materials and methods

2.1 Study design and sampling technique

The purposive sampling technique was used in sampling respondents in areas that have a history of snakebite incidence, which served as a key informant, courtesy calls was made to the chiefs of the snake charmers association with an introductory letter explaining the purpose of the study and how they can be of help. An interview was conducted comprising 18 professional snake charmers with good knowledge of snakes from various local governments in the North eastern States. Based on the outcome of the interview, ten (10) professional snake charmers were recruited to participate in the study for effective snake capture. Endemic areas were sampled as a study sites and primary data were collected through the administration of questionnaires (Figure 1).

Figure 1.

Map of the Snake endemic areas.

2.2 Questionnaire for collecting information on the local population

The quantitative part of the study was conducted in the community whereby the households were randomly selected in all three areas. Primary data were collected through a structured questionnaire. Purposive sampling was used to select the sample size in each village. To avoid the repetition of data, one questionnaire was administered to one participant from each household. Only individuals older than 18 years with a minimum of 3 years continuous stay in the village were interviewed. Gender was considered in order to accommodate 50% of women respondents. Participation was on a voluntary basis and oral consent.

The questionnaire comprises of closed-ended questions, this technique provided valuable information on circumstances where humans encountered snakes in their daily life. The following main issues were addressed in the questionnaire: (a) frequency of encounters with snakes (b) frequency of snakebites (c) knowledge that people have on snakes and (d) views and conceptions that people have on snakes. The response after snake encounters was also investigated. Different social and economic activities that expose human beings to snakebite, as well as correlation with seasonal variation with high snakes encounters, were also studied. Applying the protocol of Kipanyula and Kimaro [10] required information is generated from the data collected.

2.3 Information on snakebite cases

Data on snakebites were collected at the Kaltungo General Hospital within the period of 1 year i.e. 2018. The hospital is one of the major snakebite treatment center and serves as a referral for the neighboring States as well. Furthermore, snake anti-venom is free at this center as a result of which there is huge influx of people to the center. Information was retrieved on snakebites such as the number of snakebite cases managed by the clinic, the age of the victims, as well as the type of treatment and antivenom used, etc. Snakebite victims often came with death snakes to the hospital for identification purposes and as such specimens were preserved in 4% formalin fixative medium in order to keep the snake intact with minimum artifacts. This method has been proved to be a highly efficient way of gathering large numbers of specimens.

2.4 Morphological data

All specimens collected from both field investigations and treatment centers were examined. Some morphometric variables such as color pattern of the snake were assessed. The quantitative phospholipidosis variable such as scale pattern, number of dorsal scale rows, ventral and sub-caudal scales were noted. These entire variables were assessed for an accurate and efficient identification purpose [11].

2.4.1 Identification of the species

Specimens were identified using a key provided by Meirte [12] and the identification crosschecked with Spawls and Branch [13] and also Chippaux [3]. Common and local names were also noted. Keys that could be used to identify up to the species level from the book entitled “Snakes of Western and Central Africa” level were also referred to in the study (https://www.whitman.edu/snakekey).

3. Result

In total, 10 snake species were encountered within the span of 6 months from July to December 2018 (see Table 1). About 45 dead snakes were retrieved from snakebite victims while they were being treated in the hospital. The rest were captured by snake charmers/catchers during field surveys. Morphological characteristics were assessed for accurate identification purposes. The following snake species were identified as shown in Table 1 (Figures 2–9). The most abundant snake species is the Echis ocellantus having the highest frequency of encounters.

Family	Specie	Local Names	English	Frequency of encounter	Venomous/non venomous
Viperidae	Echisocellantus	Kububuwa/gobeda nisa	Carpet viper	28(46)	Venomous
Viperidae; Viperidae	Bitisarientans; Causus meculatus	Kasa; —	Puff adder; Night adder	13(21); 7(11)	Venomous; Venomous
Elapidae	Najanigricolis	Kumurci	Black spitting cobra	4(6.5)	Venomous
Elapidae	Najakatiensis	—	Malian cobra	2(3.2)	Venomous
Elapidae	Najanivea	—	Cape cobra	1(1.6)	Venomous
Elapidae	Dendrospis angusticep	—	Green cobra	1(1.6)	Venomous
Elapidae; Elapidae; Colubridae	D. polylepis; Naja haje; Dispholidus typus; Python sebae	Damatsiri/micinzinmata; Gansheka; -	Black mamba; Egyptian cobra; Bloomslang; Rock python	2(3.2); 1(1.6); 1(1.6); 1(1.6); 1(1.6); 61	Venomous; Venomous; Venomous; Venomous; Non venomous

Table 1.

A list of snake species of the Alkaleri, Kaltungo and Karim Lamido North-Eastern Nigeria.

Figure 2.

Cerastes cerastes (Horned viper).

Figure 3.

Pythosebae (Rock python).

Figure 4.

Naja nigricolis (Black spitting cobra).

Figure 5.

Dendrospis angusticep (Green cobra).

Figure 6.

Naja nivea (Cape cobra).

Figure 7.

Dendrospis polylepis (Black cobra).

Figure 8.

Bitis arientan (puff Adder).

Figure 9.

Echis ocellantus (Carpet viper).

The number of human snakebites cases reported at the Kaltungo snakebite treatment center in Gombe is presented in Table 2. It serves as a major free referral center for all the neighboring victims of snakebite, About 2945 snakebite cases was recorded within the year 2018, the highest snake envenoming were observed in October with 16.7%frequency while January has the least snakebite cases of 1.7%.

Months	Number of snakebite	Percentage frequency (%)
January	53	1.7
February	137	4.6
March	138	4.6
April	229	7.7
May	230	7.8
June	257	8.7
July	356	12
August	347	11.7
September	345	11.7
October	485	16.5
November	311	10.5
December	57	1.9
Total	2945	100

Table 2.

The number of snakebite cases reported At the Kaltungo general hospital over the period of one year 2018.

January happened to be the month with least incident of snake bites, while highest incident was recorded within the month of July to November. However, from July to November, the snake bites incident peaked because it is the wet season which encourages the snakes to come out from their habitats and roam because the environment and the weather is convenient for them.

The age group distribution of the reported snakebite cases is presented in the (Table 3) below and it indicated that most snakebite victims are between the age group of 0–20 (n = 1306) and 21–40 (n = 931) while the least are reported in the elderly.

Age group(years)	Number of snakebite	Percentage frequency (%)
1–20	1306	44
21–40	931	31
41–60	635	21
61 ≥	73	2.5

Table 3.

Age group distributions of snakebite cases reported At Kaltungo general hospital.

The Gender distributions of snakebite cases reported at Kaltungo General Hospital is showed in (Table 4), with 78% frequency of snakebite in males while 22%were reported in females.

Gender	Frequency of snakebite	Percentage (%)
Females	649	22
Males	2296	78
Total:	2, 945	100

Table 4.

Gender distributions of snakebite cases reported at Kaltungo General Hospital.

The result in Table 5 shows highest distribution of 36 was obtained among 21–30 years age group while the least was 2 among the oldest age groups 51–60 and 61-above years. Subject distribution according to sex was higher among male subjects (61 out of 100).Farmers happened to have higher frequency when compared with cattle rearers (44).

Variable	Kaltungo (%)	Alkaleri (%)	Karim Lamido%	Total
Age group(yrs)
18–20	14(15.5)	5(5.5)	7(7.7)	26
21–30	8(8.8)	15(15.5)	11(12.2)	33
31–40	5(5.5)	7(7.7)	8(8.8)	20
41–50	2(2.2)	2(2.2)	1(1.1)	5
51–61	0	1(1.10)	1(1.1)	4
61 above	1(1.1)	1(1.1)	0	2
Total	30	30	30	100
Sex
Male	24(26.6)	20(22.2)	27(30)	78.6
Female	6(6.5)	10(11.1)	3(3.3)	20.9
Total	30	30	30	100
Occupation
Farming	16(18)	21(23)	14(15)	56
Cattle rearers	14(15)	9(10)	16(17)	42
Total	30	30	30	100

Table 5.

Socio-demographic characteristics of respondent from Gombe (Kaltungo), Bauchi (Alkalarie) and Taraba (Karim Lamido).

Table 6 describes incident of snake bite and frequency of snake encounter by the subjects. Most of the subjects had encounter with snakes less than 10 times per month (77/100). Echisocellantus is the snake species mostly having encounter with the subjects (66/100). Rainy season is the season with more frequency of snake encounter and bites (68/100).

Variable		Kaltungo %	Alkaleri %	Karim Lamido%
Snake encountered	Few
	Highly	30(33)	30(33)	25(27.7)
	Moderately	0	0	5(5.5)
Monthly encounter	<10; 20–30; >30	19(21); 10(11.1); 1(1.1)	25(27.7); 5(5.5); 0	29(32); 1(1.1); 0
Most snake spp. encountered	Echisocellantus	28(31.1)	20(22.2)	18(20)
	Bitisarientans; Causus meculatus	1(1.1); 0	2(2.2); 1(1.1)	7(7.7); 1(1.1)
	Najanigricolis	1(1.1)	4(4.4)	3(3.3)
	Najakatiensis	0	1(1.1)	1(1.1)
	Najanivea	0	0	0
	Dendrospis angusticep	0	1(1.1); 1(1.1)	0; 0
Time of the year; Circumstance of; Bite; Site of bite; Time of bite; Snakebite treatment center; Limiting snake	D. polylepis; Naja haje; Dispholidus typus; Rainy season; Dry season; Walking; Working; Hand; Leg; Eye; Morning; Evening; Night; Yes; No; Rearing pig; killing; planting trees	0; 0; 0; 22(24.6); 8; 8; 22(24.6); 4(4.4); 26(28.8); 0; 5(5.5); 22(24.6); 2(2.2); 30(33.3); 0; 25(27.7); 5(5.5); 0	0; 0; 0; 20(22.2); 10(11.1); 14; 16; 7(7.7); 22(24.6); 1; 3(3.3); 27(30); 0; 30(33.3); 0; 23(25.5); 6(6.6); 1(1.1)	0; 0; 0; 25(27.70; 5(5.5); 5; 25(27.7); 6(6.6); 23; 1(1.1); 18(20); 12(13.3); 1(1.1); 0; 30(33.3); 28(31.1); 2(2.2); 0

Table 6.

Incidence of snakebite and encounter.

4. Discussion

In this study 10 venomous snake species were recorded in the North Eastern State of Gombe, Taraba and Bauchi which are snake endemic communities in Nigeria. The climatic condition of the region provides an ideal environment for such savannah dwelling faunas. Similar species were also reported by previous researchers based on hospital survey records [14]. It also correlates with other studies [15] where 14 venomous snakes were reported in Nigeria [16] with Naja nigrocolis, Naja melanoleuca, Causus maculatus been found in Niger Delta. North Eastern Nigeria has been designated to be haven of snake by lots of researchers as it is harboring the highest population of snakes than all other parts of the country put together [15]. Naja nigrocolis, Bitis arientans and Dendroaspis polylepis were also found in Northern Tanzania based on herpetofauna survey conducted by Kipanyula and Kimaro [10]. Interestingly, Togo harbors the highest number of snake species in Africa based on a recent herpetofauna survey it showed that about 91 snakes species were found throughout the country among which the Nigerian Naja nigrocolis, Bitis arientans and D. polylepis and Echis ocellantus were also found in the savannah region of the country [17].

The most abundant snake species obtained from the study (Table 6) is the Echis ocellantus with a frequency of 66 and it was found throughout the study area, this high abundance could be a result of the vast agricultural farmland that pests such as rodents flourished in thereby inviting their counterpart snake predators. These findings are consistence with Habib [6] that reported about 95% of snakebite morbidity and mortality to be associated Echis ocellantus. This finding also conforms with the studies carried out by other researchers [14, 18].

During the course of this study a total number of 2945 snakebite cases have been recorded within the year 2018 only. The Kaltungo General Hospital in Gombe has been and is still a major snakebite treatment center in the Northeast and served as a major referral center for all neighboring victims of snakebite. The anti-snake venom in this hospital is totally free this could be the reason behind the increased influx of snakebite victims to the Hospital. This correlates with several studies in this region that reported an average lethality of 100–150 in hospitals and an overall mortality of 15.6 daily in Kaltungo [7, 18, 19, 20].

The highest snakebite envenoming in (Table 2) was reported between the months of August to October (rainy season) with the frequency of 11.5–16%, reason might be as a result of rainy season which coincided with the peak agricultural and pastoralist activities of the people. January happened to be the month with least incident of snake bites, while highest incident was recorded within the month of July to November. This discrepancy could be due to the fact that January is a Harmattan season (a very cold and dry season) which forces all cold-blooded animals (including snakes) to hide in the caves or burrows. However, from July to November, the snake bites incident peaked because it is the wet season which encourages the snakes to come out from their habitats and roam because the environment and the weather is convenient for them. Also, most of the snakes breed in this season thereby increasing their population and thus higher contact with humans. These findings are accordance with Chippaux in 2017 that reported about 74% of hospital beds have been occupied by snakebite victims, it contradicts the study [21, 22] in forest regions bites occurs almost throughout the year.

Males are bitten more often than females as shown in (Table 3) with reported 61 male snakebite victims and 39 females. This wide gap could be a result of males being considered as breadwinners of their homes and they are mostly engaged in farming which is considered a major source of employment. The similar results have been obtained [23]. Similarly, bites are most common in children and adolescents as having the highest snake envenomation of 1306 (44%) this is as a result of they often play with their bare hands in burrows in search of small vertebrates to supplement their diet.

Based on the outcome of the questionnaire in (Table 6) 100% of the respondent from Kaltungo, Alkalarie and Bambur have encountered snakes in their life to some extent and they consider their areas to harbor the highest number of snake species. The most medically important snake species in those areas are Echis ocellantus (Carpet viper), Bitis arientans (Puff adder) and Naja nigrocolis (Black spitting copra). This has been documented in a lot of literatures [4, 7, 19, 24, 25].

The majority of snakebites as shown in (Table 6) occur either in the late afternoon or early evening, times it might occur at night while the people are sleeping. In such cases, the snakes are mostly searching for food inside houses. Interestingly according to Chippaux [4] and Habib [15] reported that some species especially Naja spp. are mostly nocturnal as such bites by such spp. are mostly at night.

Over 77 out of 100 of the bites are located on the lower limb, especially below the knee. This is because most of the bites occur during agricultural work, hunting, or movement related to work. Bites to the hand or eye are uncommon to rare, but not exceptional, especially among farmers who work with traditional tools with short handles or in children who dig or play with their bare hands in burrows in search of small vertebrates to supplement their diet. All these increases their chances of exposure to such snakes this is also in accordance with earlier workers [4, 24, 26].

5. Conclusion

Snake envenomation is increasingly recognized as a serious, worldwide public health concern and a neglected tropical disease of global importance, especially in North Eastern Nigeria. In this study, 10 venomous snake species were reported in Gombe, Taraba and Bauchi States (Figure 1). Echis ocellantus was the most abundant snake in the endemic communities. Males happened to be most affected with snake bites of 2296 (77%) more than females since they are more exposed to snakes encounter at the farms than the females. Highest snake envenoming was recorded within the month of August and October (16.1%) with least occurrence in January (1.7%).

The findings of this study will be very significant in a future studies on various applied aspects.