Multidisciplinary haematology as prognostic device in environmental and xenobiotic stress-induced response in fish

Highlights

• Haematology can evaluate normal blood cells variation by intrinsic or extrinsic factors.

• Fish blood cells alteration can be observed through eritrogram and leukogram.

• Haematological parameters can be indicator of environmental quality.

• Haematologic evaluation may assist the veterinary staff with detecting disease in fish.

• Mitochondrial activity can be a good indicator of fish health state.

• Mitochondria dysfunction may be associated with anemia development.

Abstract

The variations of haematological parameters hematocrit, hemoglobin concentration, leukocyte and erythrocyte count have been used as pollution and physiological indicators of organic dysfunction in both environmental and aquaculture studies. These parameters are commonly applied as prognostic and diagnostic tools in fish health status. However, there are both extrinsic and intrinsic factors to consider when performing a blood test, because a major limitation for field researchers is that the “rules” for animal or human haematology do not always apply to wildlife. The main objective of this review is to show how some environmental and xenobiotic factors are capable to modulating the haematic cells. Visualizing the strengths and limitations of a haematological analysis in the health assessment of wild and culture fish. Finally, we point out the importance of the use of mitochondrial activities as part of haematological evaluations associated to environment or aquaculture stress.

Introduction

Haematological evaluation in fish has been done for more than 70 years (Katz, 1951; Hesser, 1960; Blaxhall and Daisley, 1973). Notwithstanding, for a correct interpretation of fish blood cells health status is necessary to contemplate a sum of variants, such as reproductive cycle, age, sex, feeding behavior, stress, nutritional status, and water quality as well as the habitat of species, since being poikilothermic animals are under the influence of environmental changes (Bastardo and Díaz-Barberán, 2005; Gabriel et al., 2004, Gabriel et al., 2007; Satheeshkumar et al., 2012a, Satheeshkumar et al., 2012b). Furthermore, in aquaculture it is also necessary to consider the sampling technique, transportation, type of culture system, acclimation procedure, and water quality (Ezeri et al., 2004; Gabriel et al., 2004, Gabriel et al., 2007, Gabriel et al., 2011; Rey Vázquez and Guerrero, 2007; Correa-Negrete et al., 2009; Faggio et al., 2014a, Faggio et al., 2014b, Faggio et al., 2014c). On the other hand, factors such as blood collection, handling and storage time of blood samples can strongly influence the results obtained from a haematological analysis, recommending carrying out the haematological evaluations immediately after blood collection because long-term storage can modifies the results of the analyses, probably due to storage-related degenerative changes that may occur (Faggio et al., 2013; Fazio et al., 2014a).

Haematological paramters in fish including hematocrit (Hct), hemoglobin concentration (Hb), Red Blood Cell (RBC) and White Blood Cell (WBC) account, platelet count (PLT), Packed cell volume (PCV), Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), Mean Corpuscular Hemoglobin Concentration (MCHC) and sedimentation rate (Grant, 2015; Neelima et al., 2015). All these blood parameters can be influenced by intrinsic and external factors (Table 1) affecting the appearance of cells and the quantitative values obtained (Clauss et al., 2008). Differential blood cells (DBC) account, including RBC and WBC concentration, is one of the best haematological indicators of fish health because it can indicate the presence of an infectious disease (Blaxhall and Daisley, 1973; Grant, 2015) providing data for studies of defense mechanisms disease and pathogenesis (Fijan, 2002a, Fijan, 2002b). This approach has been employed in monitoring the fish health status under conditions of reproduction, nutrition, and density (Palíková et al., 1999; Pavlidis et al., 2007; Zexia et al., 2007; Burgos-Aceves et al., 2010, Burgos-Aceves et al., 2012; El-Naggar et al., 2017), or after drug administration, parasite infestations, or environmental stress (Ranzani-Paiva et al., 2008; Dias et al., 2011; Seriani et al., 2015a, Seriani et al., 2015b; Ventura et al., 2015; Corrêa et al., 2017; Grzelak et al., 2017; Valero et al., 2018). A comparative study in three cyprinid species Prussian carp Carassius gibelio, common bleak Alburnus alburnus and common rudd Scardinius erythrophthalmus showed that there were no differences in their haematological indices evaluated. Probably due to the similar living conditions of the studied species, such as their nutrition and habitat type (Nikolov and Boyadzieva-Doichinova, 2010). Therefore, the application of haematological indices is inexpensive and rapid to perform, allowing anticipating the clinical manifestations of diseases by monitoring the physiological, nutritional and health status of fish (Burgos-Aceves et al., 2010; Zorriehzahra et al., 2010). The blood and its constituents may reflect many diseases, the abnormalities of erythrocytes, leukocytes, thrombocytes, and clotting factors are considered primary blood disorders. Such aberrations in function or structure of the blood cells may result in anemia, leukopenia, leukocytosis, neutropenia, thrombocytopenia, and other blood cell abnormalities (Clauss et al., 2008). Then, to have a basic knowledge of haematology represents a valuable guide to assess the condition within the fish long before there is an outward manifestation of diseases (Rey Vázquez and Guerrero, 2007; Maheswaran et al., 2008), once reference values are established under standardized conditions (Faggio et al., 2013).