Neutralization Capacity of Tissue Alterations Caused by the Venoms of the Most Dangerous Scorpions in North Africa Using a Selective Antivenom

Abstract

In North Africa, scorpion stings pose an urgent public health problem, particularly for children with high morbidity and mortality rates. The main species implicated are the Androctonus mauretanicus (Am), Androctonus australis hector (Aah), and Buthus occitanus (Bo). Immunotherapy is the specific therapeutic approach aimed at directly neutralizing toxins, despite their severity and rapid diffusion. In the present study, we evaluate, histologically and immunohistologically, the neutralization potency of the selective antivenom produced against, among other species, the Am, Aah, and Bo at the level of the tissue alterations in Swiss mice, as experimental subjects. Firstly, the lethal doses 50 test was conducted to assess the venom's toxic activity, and then the median effective dose of the antivenom was determined against each venom. The histological and immunohistological analyses were performed by injecting the sublethal dose of venom, the complex venom and antivenom, or the antivenom 2 h following inoculation of venom. Our study revealed the highest toxicity of the Am, followed by the Aah and then the Bo venom. The neutralizing ability and effectiveness of the antivenom to completely or partially neutralize the tissular damages were demonstrated in all organs studied: brain, heart, lungs, liver, and kidneys. Our results highlighted the important cytoplasmic and membranous staining in the heart compared to the brain tissue for the three scorpion venoms. Therefore, the scorpionic antivenoms are able to reach their target even at the tissue level. Immunotherapy represents the specific and recommended treatment against the scorpionic stings in North Africa.

Keywords: immunohistochemistry; neutralization; scorpion antivenom; tissular alterations; toxicity; venom.

Figure 1

Histological observation of the brains of mice treated with the scorpion venoms (b1,b2,e,h1,h2), the complex V + AV (c,f,i), and the AV 2 h following the envenomation (d,g,j) (×10). (a): Image corresponds to the control group. (b1,b2,h1,h2): Images captured from different regions within the same histological section of the group treated with Am and Bo venoms, respectively. Bv: blood vessel; N: neuron; Hd: hemosiderin deposits; Vd: vasodilatation; Ed: edema; Lc: loss of cellularity; Hr: hemorrhage.

Figure 2

Histological observation of the hearts of mice treated with the scorpion venoms (b,e,h), the complex V + AV (c,f,i), and the AV 2 h following the envenomation (d,g,j) (×40 for the image (h) and ×10 for the rest). (a): Image corresponds to the control group. Mf: nuscle fiber; Dmf: degeneration of myocardium; Cong: congestion.

Figure 3

Histological observation of the lungs of mice treated with the scorpion venoms (b1,b2,e1,e2,h), the complex V + AV (c,f,i), and the AV 2 h following the envenomation (d,g,j) (×40 for all observations except the image (f), with ×100). (a): Image corresponds to the control group. (b1,b2,e1,e2): Images captured from different regions within the same histological section of the group treated with Am and Aah venoms, respectively. Alv: alveolar; Br: bronchi; Ad: alveolar destruction; Ase: expansion of alveolar space; Pe: pulmonary emphysema; Cong: congestion; Tp: pulmonary thrombi; Inf: inflammatory cell infiltration.

Figure 4

Histological observation of the livers of mice treated with the scorpion venoms (b1,b2,e,h), the complex V + AV (c,f,i), and the AV 2 h following the envenomation (d,g,j) (×10 for the images (b2,d,f,i,j) and ×40 for the rest). (a): Image corresponds to the control group. (b1,b2): Images captured from different regions within the same histological section of the group treated with Am venom. Hp: hepatocyte; Sn: sinusoid; Cv: central lobular vein; Esn: sinusoidal dilation; Congc: centro-lobular congestion; Congs: sinusoidal congestion; Congv: vascular congestion; Inf: inflammatory cell infiltration.

Figure 5

Histological observation of the kidneys of mice treated with the scorpion venoms (b,e,h), the complex V + AV (c,f,i), and the AV 2 h following the envenomation (d,g,j) (×10 for the images (c,f,j), and ×40 for the rest). (a): Image corresponds to the control group. Gm: glomeruli; Tl: tubular light; Gd: glomerular destruction; Elt: tubular light widening; Cong: congestion; Hr: hemorrhage.

Figure 6

Immunohistochemical detection of Am venom (B) and the complex venom–antivenom (C,D) in nerve tissue. (A): The control group. The calibration bar = 50 µm. Bv: blood vessel. Brown areas are positive for venom and complex venom–antivenom. Detection in nerve cells (red arrow) and vascular endothelial cells (black arrow).

Figure 7

Immunohistochemical detection of Am venom (L) and the complex venom–antivenom (M,N) in cardiac tissue. (K): The control group. Calibration bar = 50 µm. Brown areas are positive for venom and complex venom–antivenom. Detection in vascular endothelial cells (black arrow), myocardial muscle cells (blue arrow), and inflammatory cells (green arrow).

Figure 8

Immunohistochemical detection of Aah venom (E) and the complex venom–antivenom (F,G) in nerve tissue. (A): The control group. Calibration bar = 50 µm. Brown areas are positive for venom and complex venom–antivenom. Detection in nerve cells (red arrow), vascular endothelial cells (black arrow), and inflammatory cells (green arrow).

Figure 9

Immunohistochemical detection of Aah venom (O) and the complex venom–antivenom (P,Q) cardiac tissue. (K): The control group. Calibration bar = 50 µm. Brown areas are positive for venom and complex venom–antivenom. Detection in vascular endothelial cells (black arrow) and myocardial muscle cells (blue arrow), and inflammatory cells (green arrow).

Figure 10

Immunohistochemical detection of Bo venom (H) and the complex venom–antivenom (I,J) in nerve tissue. (A): The control group. Calibration bar = 50 µm. Brown areas are positive for venom and complex venom–antivenom. Detection in nerve cells (red arrow).

Figure 11

Immunohistochemical detection of Bo venom (R) and the complex venom–antivenom (S,T) in cardiac tissue. (K): The control group. Calibration bar = 50 µm. Brown areas are positive for venom and complex venom–antivenom. Detection in vascular endothelial cells (black arrow), myocardial muscle cells (blue arrow), and inflammatory cells (green arrow).