Hematological and immune changes in Piaractus mesopotamicus in the sepsis induced by Aeromonas hydrophila

doi:10.1016/j.fsi.2019.01.044

Fish & Shellfish Immunology

Volume 88, May 2019, Pages 259-265

https://doi.org/10.1016/j.fsi.2019.01.044 Get rights and content

Highlights

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A. hydrophila induced hematological and immune changes in P. mesopotamicus.
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Leukocytes and thrombocytes alterations were associated in the sepsis.
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A. hydrophila is a potent immunogenic and has high lethality in P. mesopotamicus.
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P. mesopotamicus is susceptible to sepsis and septic shock.

Abstract

The pathogenesis of sepsis involves complex systems and multiple interrelationships between the host and pathogen producing high mortality rates in various animal species. In this study, hematological disturbances, innate immunity and survival during the septic process in Piaractus mesopotamicus inoculated with Aeromonas hydrophila were studied. For this aim, fish blood samples were taken from control and infected groups 1, 3, 6, and 9 h post-inoculation (HPI). Leukogram showed reduction in the number of leukocytes and thrombocytes, followed by cessation of leukocyte chemotaxis 6 HPI and severe morphological changes in leukocytes and erythrocytes. At 3 HPI production of reactive oxygen species increased and at 6 HPI decreased. There was no change in serum lysozyme concentration and lytic activity of the complement system, despite the progressive increase in serum lytic activity and bacterial agglutination. Finally, the changes in clinical signs due to aeromonosis and increasing septicemia resulted in a reduction in survival to 57.14% after 36 HPI. It was possible concluded that these hematological and immune are crucial event in the worsening of sepsis in P. mesopotamicus, and these findings are utility for diagnosing and understanding the pathophysiology sepsis in pacu induced by A. hydrophila.

Introduction

Gram-negative sepsis is triggered by the activation of the immune and endothelial cells by infectious agents [1] mainly when endotoxins (LPS) are contacted to host monocytes and macrophages [2]. This response is complex, exacerbated and uncontrolled that leads to high rates of morbidity and mortality [3,4] altering inflammation response, hematological profile and morphology of leucocytes [5].

Unlike endothermic animals, ectothermic vertebrates are tolerant to endotoxic shock [6]. However, endotoxins are responsible for the pathogenicity of Gram-negative bacteria in several fish species [7,8]. Aeromonas hydrophila is an ubiquitous Gram-negative pathogen that causes extensive economic losses especially in intensive fish farming worldwide. This bacteria cause septic outbreaks with high mortality rates in several animal species and poses a serious threat to public health [9].

Piaractus mesopotamicus is a fish endemic to Parana-Paraguay Basin, and it is currently one of the most widely cultivated fish species in South America. It also has a great potential for aquaculture due to its characteristics [10,11]. In this context, it was studied the hematological disturbances, innate immunity and survival of fish during the evolution of the septic process in Piaractus mesopotamicus inoculated with Aeromonas hydrophila a potent immunogenic and has high lethality in this species of fish.

Section snippets

Fish

A total of 144 pacus, P. mesopotamicus, from a commercial farm were used (180.71 ± 38.1 g/21.27 ± 6.7 cm), acclimatized during seven days in 18 fiber boxes (n = 8/250 L), filled with artesian well water (1 L/min flow) and constant aeration. Fish were fed with commercial diet (3% of biomass, 28% of crude protein and 4000 kcal of crude energy kg⁻¹) [11]. The study was carried out according to the Brazilian animal welfare standards and ISO - International Organization for Standardization (2006)

Blood count and total serum proteins

The evaluation of blood components of septic pacus was divided into erythrogram, leukogram and total plasma proteins. In the erythrogram was verified that at 9 HPI the mean globular volume increased (p < 0.05) in relation to control group. For others erythrocyte parameters analyzed, it was not observed differences (p > 0.05; Table 1).

Lymphocytes, monocytes, granulocytes (neutrophils and special granulocytic cells), thrombocytes, and eosinophils were observed on examination of the blood

Discussion

Sepsis was induced by inoculation of A. hydrophila into pacus. This was evidenced by the hematological and immune changes, and the positive blood culture in blood. The cumulative effect of these changes led to clinical signs and decreased survival of fish. These data are similar to those found in different species of teleosts afflicted by Gram-positive and Gram-negative infections [8,28]. However, it was observed that at least 30% of the inoculated animals were resistant and/or tolerant to A.

Acknowledgements

The authors are grateful for the support of the São Paulo State Research Support Foundation - FAPESP projects n° 2014/10231-2 and 2011/20280-2 and the National Council for Scientific and Technological Development - CNPq (process 441054/2014-5). In Memoriam: A Great Friend and Mentor, Professor Flávio Ruas de Moraes.

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Full length articleHematological and immune changes in Piaractus mesopotamicus in the sepsis induced by Aeromonas hydrophila

Highlights

Abstract

Introduction

Section snippets

Fish

Blood count and total serum proteins

Discussion

Acknowledgements

Fish Shellfish Immunol.

J. Comp. Pathol.

Aquaculture

Fish Shellfish Immunol.

Fish Shellfish Immunol.

Immunity

Semin. Immunol.

J. Pediatr.

Fish Shellfish Immunol.

Fish Shellfish Immunol.

Fish Shellfish Immunol.

Fish Shellfish Immunol.

Innate immune responses to danger signals in systemic inflammatory response syndrome and sepsis

Scand. J. Immunol.

Plasma interleukin-6 response is predictive for severity and mortality in canine systemic inflammatory response 86 syndrome and sepsis

Vet. Clin. Pathol.

2001 SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference

Crit. Care Med.

Robbins & Cotran Pathologic Basis of Disease

Host innate immune responses to sepsis

Virulence

Bacterial lipopolysaccharide induces apoptosis in the trout ovary

Reprod. Biol. Endocrinol.

Morphologic disorders in leukocytes of goldfish sample (Carassius auratus auratus Linnaeus, 1758) with bacterial hemorrhagic septicemia: case report

R. bras. Ci. Vet.

Virulence factor activity relationships (VFARs) with specific emphasis on Aeromonas species

J. Water Health

Acute toxicity by water containing hexavalent or trivalente chromium in native Brazilian fish, Piaractus mesopotamicus: anatomopathological alterations and mortality

Bull. Environ. Contam. Toxicol.

Water Quality in Ponds for Aquaculture, Alabama Agricultural Experiment Station

Hematology and clinical signs of Piaractus mesopotamicus experimentally infected with Aeromonas hydrophila

Acta Scientiarum Acta Sci

Full length article
Hematological and immune changes in Piaractus mesopotamicus in the sepsis induced by Aeromonas hydrophila