Pathology and causes of death in stranded humpback whales (Megaptera novaeangliae) from Brazil

Abstract

This study describes the pathologic findings of 24 humpback whales (Megaptera novaeangliae) found stranded along the Brazilian coast from 2004 to 2016. Eighteen (75%) animals evaluated were found stranded alive. From these, 13 died naturally on shore and five were euthanized. Six died at sea and were washed ashore. Of the 24, 19 (79.2%) were calves, four (16.7%) were juveniles, and one (4.2%) was an adult. The most probable cause of stranding and/or death (CSD) was determined in 23/24 (95.8%) individuals. In calves, CSD included neonatal respiratory distress (13/19; 68.4%), infectious disease (septicemia, omphaloarteritis and urachocystitis; 3/19; 15.8%), trauma of unknown origin (2/19; 10.5%), and vehicular trauma (vessel strike; 1/19; 5.3%). In juveniles and adult individuals, CSD was: emaciation (2/5; 40%), sunlight-thermal burn shock (1/5; 20%); and discospondylitis (1/5; 20%). In one juvenile, the CSD was undetermined (1/5; 20%). This study integrates novel findings and published case reports to delineate the pathology of a South-western Atlantic population of humpback whales. This foundation will aid in the assessment of the population health and establish a baseline for development of conservation policies.

Pathologic findings and causes of death of stranded cetaceans in the Canary Islands (2006-2012)

“…For instance, some studies reported only bacterial infections [ 85 ], and others considered viral, bacterial, fungal and parasitic processes altogether [ 4 ]. Nonetheless, when most studies from other geographical areas are scrutinized our data show similar or higher prevalence of infectious disease [ 4 , 12 , 79 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 ].…”

“…NPP in cetaceans may include: abortion, dystocia, early maternal-filial separation or maternal neglect, early fatal intra- and interspecific interactions, infections, loss of passive transfer immunity, prematurity, and congenital malformations, among others [ 12 , 86 ]. Disturbances during gestation, labor, lactation and early behavioral abnormalities may be also included in this category [ 12 , 86 ]. We observed evidences of fetal distress (46%), dystocia (15%), infectious (15%), abortion (7.7%), congenital malformation (7.7%) and neonatal maternal-filial separation/maternal neglect (7.7%).…”

“…Our results suggest that fetal distress, based on compatible gross and histologic findings (e.g., pulmonary edema, aspirated squames and/or meconium, hyaline membranes) occurs in this category, regardless the primary underlying cause. Thus, perinatal respiratory distress or asphyxia is a common pathogenic mechanism in NPP-fatalities in cetaceans [ 86 ]. We also observed a case of presumed dystocia and of presumed maternal-filial separation.…”

Diseases and parasites

“…With the exception of one unusual case of granulomatous myocarditis (NSB-DWM 2002B3; Stimmelmayr, 2015 ) with apparent gross lesions in a mature female bowhead whale, the remainder of myocardial lesions including myocardial contraction band necrosis (CBN) and interstitial myocarditis were strictly histological findings. CBN is part of a suite of pathological changes (myocardial renal lesions) brought on by massive catecholamine release (alarm reaction) in stranded cetaceans ( Cowan and Curry, 2008 , Groch et al, 2018 ). Respiratory lesions recorded in bowhead whales include isolated observations of lesions likely indicative of previous inflammatory processes of viral, parasitic or bacterial origin (i.e., alveolar histiocytosis; interstitial fibrosis; bronchopneumonia; interstitial pneumonia; pleural fibrosis; angiomatosis).…”

Skeletal and Cardiac Rhabdomyolysis in a Live-Stranded Neonatal Bryde's Whale With Fetal Distress

“…The importance of these studies is recognized worldwide to promote conservation of these animals. Unfortunately, the description of pathological entities and/or causes of death in the infraorder Mysticeti remains rare (1)(2)(3)(4)(5)(6)(7)(8).…”