Pathological Findings in Leatherback Sea Turtles (Dermochelys coriacea) During an Unusual Mortality Event in São Paulo, Brazil, in 2016.

The leatherback sea turtle (LST; Dermochelys coriacea) is highly migratory and is primarily distributed throughout tropical and subtropical regions. The LST populations found in Brazil are critically endangered. An unusual mortality event occurred between August and November 2016 with 23 LSTs stranded along a 100 km coastal segment in Iguape, Ilha Comprida and Ilha do Cardoso in southern São Paulo state. This study investigated the pathological findings and most likely causes of death of 10 LSTs. Male (n = 9) and adult (n = 9) animals predominated. All but one animal was in good body condition and all were found dead. The most prevalent gross findings were suggestive of bycatch, namely cutaneous erosions, abrasions and/or lacerations around the neck and flippers (n = 9), generalized congestion (n = 8) and pulmonary oedema (n = 6). Other prevalent gross findings were: cutaneous epibiosis by Stomatolepas elegans (n = 7); ileocecal diverticulitis (n = 7); distal oesophagitis (n = 5); and fibrinous coelomitis (n = 5). Microscopically, the most prevalent findings were: hepatic melanomacrophage centre hypertrophy or hyperplasia (n = 9); interstitial pneumonia (n = 8); multisystemic congestion (n = 6); pulmonary oedema with or without aspirated material (n = 5); adrenal coccidiosis (n = 5) with variable multiorgan involvement; and multiorgan bacterial disease (n = 5). Five animals had food ingesta (cnidarians, crustaceans) in the oesophagus or stomach; only one had evident plastic foreign bodies. Asphyxia due to entanglement in nets was the most frequently identified cause of death (n = 8); a cause of death was not identified in two animals. Our findings provide evidence of the severe negative impact of entanglement in fishing nets in LSTs, raising concerns for conservation. These findings also contribute to knowledge of the pathology of LSTs in South American populations.

Presence of antibodies against the third intracellular loop of the m2 muscarinic receptor in the sera of chronic chagasic patients.

Patients in the chronic phase of Chagas' disease suffer from a slowly evolving inflammatory cardiomyopathy that can lead to severe cardiac dilatation, congestive heart failure, and death. This process appears to be caused by autoimmune recognition of heart tissue by a mononuclear cell infiltrate decades after infection with the parasite Trypanosoma cruzi. Recent evidence suggests that there are circulating antibodies in chronic chagasic patients that alter the physiological behavior of the heart on binding to G-protein-coupled cardiovascular receptors, including beta1-adrenergic and m2 muscarinic receptors. A 42 kDa fusion protein was constructed that contains the central part of the third intracellular loop (i3; Arg(267)-Arg(381)) of the human m2 muscarinic receptor, linked to glutathione S-transferase. This fusion protein was overexpressed in Escherichia coli and subsequently purified by affinity chromatography. Based on Western blots, the i3 loop is specifically recognized by the sera of chronic chagasic patients who have reached advanced stages of cardiac failure (according to the Los Andes classification). Analysis of the prevalence and distribution of these antibodies shows a strong association between seropositive patients and moderate (group II) to severe (group III) heart dysfunction.

Functionally active cardiac antibodies in chronic Chagas' disease are specifically blocked by Trypanosoma cruzi antigens.

Antibodies of chronic chagasic patients have been shown to interfere with electric and mechanical activities of cardiac embryonic myocytes in culture and with whole mammalian hearts. A mechanism proposed for this effect involves interaction of the antibodies with G-protein-linked membrane receptors, thus leading to activation of beta adrenergic and muscarinic receptors; more specifically, IgG of chagasic patients would interact with the negatively charged regions of the second extracellular loop of these receptors. We performed competition experiments to test this hypothesis. We evaluated the effect of sera/IgG from patients previously known to depress electrogenesis and/or atrioventricular conduction in isolated rabbit hearts after incubation with live and lysed parasites, the peptide corresponding to the second extracellular loop (O2) of the M2 receptor, and different peptides derived from two ribosomal proteins of T. cruzi: P0 and P2beta. Our results indicate that 1) the antigenic factor inducing the functionally active IgGs in the chagasic patients is probably an intracellular T. cruzi antigen; 2) IgG/serum is interacting with the O2 region of the M2 receptor in the rabbit heart; and 3) the negative charges present in the ribosomal proteins of T. cruzi are important in mediating the interaction between the patients' serum/IgG and the receptor.