BackgroundIn Yucatán State, southern México, as in many other parts of the world where tilapia has been introduced for aquaculture, the deficient application of management measures has led to the establishment of non-native parasites. The aims of this study were to describe the geographical distribution of protozoan and helminth parasites of farmed Nile tilapia Oreochromis niloticus (L.) throughout the Yucatán and to examine the potential statistical associations of the prevalence and mean abundance of these parasites with management and environmental variables.MethodsAll 29 Nile tilapia farms currently operating in Yucatán were surveyed. Maps were created to describe the geographical location of the parasites infecting Nile tilapia at each farm. We evaluated the statistical associations of management and environmental variables with the mean abundance values of each parasite species using a multivariate redundancy analysis (RDA) and generalized additive models (GAM). We also used Ripley’s K to determine whether there were significant clusters of the mean abundance of particular parasite species in specific regions of the Yucatán State.ResultsA total of 580 O. niloticus were examined, and 11 species of parasites were recorded. Cichlidogyrus sclerosus was the most frequent and abundant parasite at all 29 farms, whereas Gyrodactylus cichlidarum was found in 26 of the 29 farms. The RDA showed that the most important predictors were the concentration of nitrites and ammonium and the water exchange rate. The GAM showed the significant effect of the tank capacity, no use of quarantine area and no use of prophylactic treatments on the mean abundance of G. cichlidarum. The geographical distribution patterns of the mean abundance of most parasite species exhibited clustering near to the coast of Yucatán.ConclusionTwo groups of farms were distinguished: (i) farms with medium to high technology, where the most frequent and abundant parasite was G. cichlidarum, and (ii) farms with low technology, where the most frequent and abundant parasite was C. sclerosus. Good biosecurity practices such as the use of quarantine and prophylactic treatments prior to the introduction of infected Nile tilapia to the farms are recommended to avoid the establishment of parasites such as G. cichlidarum in farms.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1332-9) contains supplementary material, which is available to authorized users.

Latin America has tripled production by aquaculture up to 78 million tonnes in the past 20 years. However, one of the problems that aquaculture is facing is the presence of helminth parasites and the diseases caused by them in the region. In this review we have collected all the available information on helminths affecting commercial aquaculture in Latin America and the Caribbean (LAC), emphasizing those causing serious economic losses. Monogeneans are by far the most common and aggressive parasites affecting farmed fish in LAC. They have been recognized as serious pathogens in intensive fish culture because they reach high levels of infection rapidly, and can infect other phylogenetically related fish species. The next most important group comprises the larval stages of digeneans (metacercariae) such as Diplostomum sp. and Centrocestus formosanus, which cause serious damage to farmed fish. Since LAC aquaculture has been based mainly on exotic species (tilapia, salmon, trout and carp), most of their parasites have been brought into the region together with the fish for aquaculture. Recently, one of us (A.I.P.-T.) has suggested that monogeneans, which have generally been considered to be harmless, can produce serious effects on the growth of cultured Nile tilapia. Therefore, the introduction of fish together with their 'harmless' parasites into new sites, regions or countries in LAC should be considered a breakdown of biosecurity in those countries involved. Therefore, the application of quarantine procedures and preventive therapeutic treatments should be considered before allowing these introductions into a country.

The cyclopoid copepod Neoergasilus japonicus ( Harada, 1930 ) is recorded from three endangered or threatened fish species from southeast Mexico: the tailbar cichlid Vieja hartwegi (Taylor and Miller, 1980); the Angostura cichlid V. breidohri (Werner and Stawikowski, 1987); and the sieve cichlid C. grammodes (Taylor and Miller, 1980). This ectoparasitic copepod is considered, together with most other members of Neoergasilus, an Eastern Asian form. N. japonicus is one of the most widespread parasitic Asian copepods, as it has rapidly invaded Europe and North America, including Mexico. We estimated the prevalence, mean abundance, and intensity of infection of N. japonicus in these cichlid teleosts; our data agree with previous works stating the high prevalence of this ectoparasite. This copepod has a wide range of hosts among freshwater fish taxa, but this is only the second published report from cichlids in the Neotropical region. The three cichlids surveyed, V. hartwegi, V. breidohri, and C. grammodes, are new hosts of this copepod. Its occurrence in Mexico is attributed to different events of introduction by human agency. This is the southernmost record of N. japonicus in continental America. It is a matter of concern that this copepod is parasitizing endangered or threatened endemic cichlids in the Neotropical region. Because its high infective efficiency and ability to shift hosts, this Asian parasite is expected to spread farther southwards into Central and South America.

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SummaryWe recorded the metazoan parasite communities in three endemic cichlids (Chiapaheros grammodes, Vieja breidohri and V. hartwegi) collected between November 2008 and July 2009 in the upper Grijalva River Basin (GRB), Chiapas, Mexico. In total, 6,287 individual parasites belonging to 18 taxa (1 monogenean, 6 digeneans, 1 cestode, 4 nematodes, 2 acanthocephalans, 1 hirudinean, 2 copepods and 1 pentastomid) were found. Eleven metazoans were adult forms and 7 larvae; moreover, 14 were endoparasites and 4 ectoparasites. Sixteen parasite taxa represent new geographical and host records. The helminth community in the three cichlids was characterized by higher number of generalists than specialists, as well as a higher proportion of autogenics than allogenics. The metazoan parasites showed prevalence and mean abundances moderate to high. The infracommunities and component community of metazoan parasites had low diversity, richness, and number of individuals and are similar to those reported for other cichlids in Southeastern Mexico, characterized by the presence of typical parasites of cichlids, with a high number of digeneans and generalist parasites. We report the introduced Asian parasitic copepod Neoergasilus japonicus parasitizing endangered or threatened endemic cichlids in the upper GRB. This copepod have been widespread in other freshwater fish species, mainly in Asia (China, India, Japan, Russia, Taiwan), Europe (France, Hungary, Italy, Turkey), and America (Cuba, Mexico, Peru, United States).

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We detected N. girellae infections in 40 species belonging to 12 families of imported marine ornamental fish from a public aquarium in the Mexican state of Yucatan in January 2018 to December 2020 and carried out their identification to the species level using morphological and molecular analyses. Monogeneans were corroborated morphologically and molecularly using a partial sequence of 28S (region D1–D3) ribosomal DNA and analyzed in a molecular phylogenetic context in combination with data derived from other species of N. girellae available in GenBank. The phylogenetic tree revealed that the specimen found consistently belonged to the N. girellae clade. High infection parameters were detected of N. girellae in the hosts. This identification is relevant to aquarists and aquaculturists in the Gulf of Mexico because N. girellae is considered highly pathogenic in confined fish. Clearly, this work demonstrates that the importation of ornamental fish, coupled with deficient sanitary measures (lack of quarantine areas in distribution centres) contributes to the introduction of parasites and their establishment and dispersal within Mexico.

La tilapia, originaria de África, ha sido introducida en cientos de países con fines de cultivo, generando un importante mercado, cubriendo necesidades alimentarias de amplios sectores de la población. La introducción de la tilapia ha traído problemas de invasiones en prácticamente todos los ambientes acuáticos tropicales de América y otros continentes, afectando la biodiversidad. Su cultivo ha generado necesidad de agua en altas cantidades, por lo que frecuentemente se emplean aguas poco aptas y sin tratamiento previo; además el agua que se emplea en los cultivos comúnmente es regresada al medio sin ningún tratamiento agudizando el problema. La mala calidad del agua produce estrés en los peces, volviéndolos susceptibles a enfermedades parasitarias, produciendo bajos rendimientos y mortalidad. Otro problema que se enfrenta respecto a las enfermedades parasitarias es la falta de conocimiento de los productores para identificar, prevenir y contrarrestar estas enfermedades. La capacitación y seguimiento de las actividades acuícolas por parte de expertos, así como compartir experiencias es fundamental para reducir estos riesgos. Existen miles de artículos científicos y técnicos que abordan estas problemáticas, pero la mayoría no está al alcance de los productores que, al no estar preparados para el manejo y control de enfermedades, sufren pérdidas económicas y desmotivación. El objetivo de este ensayo es dar al lector una visión general de la relación entre el manejo, calidad del agua y diversas enfermedades parasitarias que atacan a la tilapia en las prácticas de cultivo.