A clinical epidemiological onsite study of a massive outbreak of Scombroid fish poisoning after consumption of yellowtail kingfish in northern Chile

Scombroid fish poisoning (SFP) is an acute illness caused by the consumption of poorly preserved fish containing high levels of histamine. Symptoms develop within 1-2 h, with gastrointestinal, dermatologic, and cardiopulmonary manifestations. The diagnosis relies exclusively on the clinical picture. To describe an onsite clinical-epidemiological study of a massive outbreak of SFP occurring in Chile. Descriptive study of an outbreak occurring in a closed Convention Center after lunch with Chilean Palometa or Seriola lalandi (Yellowtail kingfish). An Onsite questionnaire was answered by all attendants within 24 h. Local health officials supervised the place with a second survey and sample recollection of suspected fish. Eighty-three adults attended the event, of which 81 ate fish. Mean age: 58.5 years old, 82.7% women. The symptomatic attack rate of people eating suspected poisoned fish was 79% (64 out of 81 participants). Most common symptoms included: diarrhea (68%); headache (64%); flushing (64%) and diffuse redness (56%). Mean incubation period: 77 min (30-240 min). 98.4% of patients recovered within 10 h. Ten patients were referred to the emergency room, but none were admitted. There was a presumption of loss of refrigeration in the handling of fish, and confirmation of SFP by clinical basis, incubation period and attack rate. Fish was the only food item associated with illness (Odds ratio: 19, p = 0.014; Fisher two tails). This is one of the 5 largest outbreaks of SFP with fresh fish, ever reported in the literature. The clinical picture and rapid onset of symptoms made it possible to suspect SFP allowing timely management of patients. It is relevant to spread the knowledge about this underdiagnosed and underreported syndrome.

First Report of Blood Fluke Pathogens with Potential Risk for Emerging Yellowtail Kingfish (Seriola lalandi) Aquaculture on the Chilean Coast, with Descriptions of Two New Species of Paradeontacylix (Aporocotylidae)

Blood flukes are digeneans that infect wild and farmed fish that can cause a severe and potentially lethal disease in farmed fish. These parasites are undetectable in the larval stage based on macroscopic observations in the definitive host with the infection becoming evident when eggs accumulate in the branchial vessels. There are nine known species of the genus Paradeontacylix and seven exclusively parasitize Seriola spp. from several geographical areas. Seriola lalandi aquaculture farms are emerging at various localities in northern Chile. Here, we report, for the first time, two blood fluke species parasitizing S. lalandi in the Southeastern Pacific (Chile). In the laboratory, the gills and heart of fish were removed. The retained blood flukes were separated according to the infection site, fixed in 70% or 95% ethanol for taxonomic and molecular analysis, respectively. Morphometrical differences among the fluke species were evaluated with a principal component analysis (PCA) using proportional body measurements. Phylogenetic trees were constructed based on 28S rDNA, cox1 mDNA using Bayesian inference (BI), and maximum likelihood (ML). Based on morphology, morphometry, and molecular analyses, two new species are proposed: P. humboldti n. sp. from the gills and P. olivai n. sp. from the heart of S. lalandi. Both were clearly distinguished from other species of Paradeontacylix by a combination of morphologic features (posterior tegumental spines, testes arrangement, body size). The genetic distance (based on cox1) among species was >10%. P. humboldti n. sp. and P. olivai n. sp. are sister species (with a common ancestor) independent of P. godfreyi from S. lalandi in Australia. The newly identified parasites may pose a risk to farmed S. lalandi as aporocotylids have been the cause of diseases in farmed fish from other geographical areas. In addition, some cages of S. lalandi are currently maintained in an open circulating system, which could favor the transmission of these parasites (if involved hosts are present in the environment).