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First record of Neoechinorhynchus buttnerae and Piscinoodinium pillulare infection in Colossoma macropomum in the state of Tocantins, Brazil

Primeiro registro de infecção por Neoechinorhynchus buttnerae e Piscinoodinium pillulare em Colossoma macropomum no estado do Tocantins, Brasil

Abstract

This study aims to report the occurrence of two important parasites in farmed tambaqui Colossoma macropomum in the state of Tocantins, the acanthocephalan Neoechinorhynchus buttnerae and the dinoflagellate protozoan Piscinoodinium pillulare, also suggesting the main treatments to control them. The fish sampled for the study were infected by N. buttnerae, and P. pillulare, with prevalence from 100% and mean intensity from 51.4 to 354,264, respectively. This was the first report on the occurrence of such parasites in C. macropomum in the state of Tocantins. We emphasize the need to adopt good farm management and biosecurity practices to prevent pathogenic agents to enter or leave a property. Reported treatments with synthetic and natural products with positive results are also suggested to treat against those parasites in farmed C. macropomum.

Keywords:
Acanthocephalan; aquaculture; fish parasites; protozoans

Resumo

Este estudo teve como objetivo relatar a ocorrência de dois importantes parasitos em tambaqui Colossoma macropomum cultivado no estado de Tocantins, o acantocéfalo Neoechinorhynchus buttnerae e o protozoário dinoflagelado Piscinoodinium pillulare e também destacar os principais tratamentos para controlá-los. Os peixes examinados estavam infectados por N. buttnerae e P. pillulare, com prevalência de 100% e intensidade média de 51,4 a 354.264,4, respectivamente. Este foi o primeiro relato da ocorrência desses parasitos para C. macropomum no estado de Tocantins. Destaca-se a necessidade da adoção de boas práticas de manejo na produção e de manejo sanitário, para evitar a contaminação da propriedade e a transmissão para pisciculturas vizinhas. Em relação ao controle dessas parasitoses são apresentados os tratamentos com resultados positivos para C. macropomum, com o uso de produtos sintéticos e naturais.

Palavras-chaves:
Acantocéfalo; aquicultura; parasitos de peixe; protozoário

Introduction

Colossoma macropomum (tambaqui) is a Serrasalminae fish species native to the Amazon and Orinoco rivers and their tributaries (Gomes et al., 2020Gomes LC, Simões LN, Araújo-Lima CARM. Tambaqui (Colossoma macropomum). In: Baldisseroto B, Gomes LC, editors. Espécies nativas para piscicultura no Brasil. 3. ed. Santa Maria: Editora UFSM; 2020. p. 17-56.; Hilsdorf et al., 2022Hilsdorf AWS, Hallerman E, Valladão GMR, Zaminhan-Hassemer M, Hashimoto DT, Dairiki JK, et al. The farming and husbandry of Colossoma macropomum: from Amazonian waters to sustainable production. Rev Aquacult 2022; 14(2): 993-1027. http://dx.doi.org/10.1111/raq.12638.
http://dx.doi.org/10.1111/raq.12638...
). It is an economically important fishery in the regions they occur naturally, as well as for aquaculture in Brazil and other Amazonian nations (Hilsdorf et al., 2022Hilsdorf AWS, Hallerman E, Valladão GMR, Zaminhan-Hassemer M, Hashimoto DT, Dairiki JK, et al. The farming and husbandry of Colossoma macropomum: from Amazonian waters to sustainable production. Rev Aquacult 2022; 14(2): 993-1027. http://dx.doi.org/10.1111/raq.12638.
http://dx.doi.org/10.1111/raq.12638...
), and in Asian countries (Woynárovich & Van Anrooy, 2019Woynárovich A, Van Anrooy R. Field guide to the culture of tambaqui Colossoma macropomum, Cuvier, 1816. FAO Fish Aquac Tech Pap 2019; 624: 1-121.). Tambaqui is the most farmed native fish species in Brazil, mainly in the Northem, Northeastern and Western regions, accounting for 262,370 tonnes and 31.2% of the national production in 2021 (Associação Brasileira da Piscicultura - PeixeBR, 2022Associação Brasileira da Piscicultura - PeixeBR. Anuário Peixe BR de piscicultura 2022 [online]. 2022 [cited 2022 Aug 20]. Available form: https://www.peixebr.com.br/anuario2022
https://www.peixebr.com.br/anuario2022...
). Tambaqui is suitable for aquaculture because of its hardiness, tolerance to low dissolved oxygen levels and high ammonia concentration in water, induced artificial spawning up to twice a year per female and easy production of juvenile fish (Valladão et al., 2018Valladão GMR, Gallani SU, Pilarski F. South American fish for continental aquaculture. Rev Aquacult 2018; 10(2): 351-369. http://dx.doi.org/10.1111/raq.12164.
http://dx.doi.org/10.1111/raq.12164...
; Gomes et al., 2020Gomes LC, Simões LN, Araújo-Lima CARM. Tambaqui (Colossoma macropomum). In: Baldisseroto B, Gomes LC, editors. Espécies nativas para piscicultura no Brasil. 3. ed. Santa Maria: Editora UFSM; 2020. p. 17-56.; Neves et al., 2020Neves LC, Favero GC, Beier SL, Ferreira NS, Palheta GDA, Melo NFAC, et al. Physiological and metabolic responses in juvenile Colossoma macropomum exposed to hypoxia. Fish Physiol Biochem 2020; 46(6): 2157-2167. http://dx.doi.org/10.1007/s10695-020-00868-8. PMid:32862281.
http://dx.doi.org/10.1007/s10695-020-008...
; Val & Oliveira, 2021Val AL, Oliveira AM. Colossoma macropomum- a tropical fish model for biology and aquaculture. J Exp Zool A Ecol Integr Physiol 2021; 335(9-10): 761-770. http://dx.doi.org/10.1002/jez.2536. PMid:34382751.
http://dx.doi.org/10.1002/jez.2536...
). Additionally, they grow fast and have high market acceptance, which all explains the first position of this native species in the national and international aquaculture (Hilsdorf et al., 2022Hilsdorf AWS, Hallerman E, Valladão GMR, Zaminhan-Hassemer M, Hashimoto DT, Dairiki JK, et al. The farming and husbandry of Colossoma macropomum: from Amazonian waters to sustainable production. Rev Aquacult 2022; 14(2): 993-1027. http://dx.doi.org/10.1111/raq.12638.
http://dx.doi.org/10.1111/raq.12638...
). The omnivorous feeding habit, acceptance of pelleted feed and intake of the natural food available in the grow-out ponds justify the adoption of the semi-intensive farming system (Valenti et al., 2021Valenti WC, Barros HP, Moraes-Valenti P, Bueno GW, Cavalli RO. Aquaculture in Brazil: past, present and future. Aquacult Rep 2021; 19: 100611. http://dx.doi.org/10.1016/j.aqrep.2021.100611.
http://dx.doi.org/10.1016/j.aqrep.2021.1...
; Hilsdorf et al., 2022Hilsdorf AWS, Hallerman E, Valladão GMR, Zaminhan-Hassemer M, Hashimoto DT, Dairiki JK, et al. The farming and husbandry of Colossoma macropomum: from Amazonian waters to sustainable production. Rev Aquacult 2022; 14(2): 993-1027. http://dx.doi.org/10.1111/raq.12638.
http://dx.doi.org/10.1111/raq.12638...
). Semi-intensive grow-out in earthen ponds is the most practiced farming system for tambaqui, in one or two phases, in mono- or polyculture and, less frequently, in cages (Pedroza-Filho et al., 2016Pedroza-Filho MX, Rodrigues APO, Rezende FP. Dinâmica da produção de tambaqui e demais peixes redondos no Brasil. Brasília, DF: CNA Bras. Ativos Aquicultura; 2016.; Valenti et al., 2021Valenti WC, Barros HP, Moraes-Valenti P, Bueno GW, Cavalli RO. Aquaculture in Brazil: past, present and future. Aquacult Rep 2021; 19: 100611. http://dx.doi.org/10.1016/j.aqrep.2021.100611.
http://dx.doi.org/10.1016/j.aqrep.2021.1...
). The direct stocking of tambaqui fingerlings of 2 to 5 g at a density of 0.4 to 0.7 fish/m2 for 12 months is the most adopted practice in the Brazilian farms according to Valenti et al. (2021)Valenti WC, Barros HP, Moraes-Valenti P, Bueno GW, Cavalli RO. Aquaculture in Brazil: past, present and future. Aquacult Rep 2021; 19: 100611. http://dx.doi.org/10.1016/j.aqrep.2021.100611.
http://dx.doi.org/10.1016/j.aqrep.2021.1...
. However, intensive systems with continuous or supplementary use of aerators are also adopted to increase productivity and shorten the cycle to 10 months (Izel et al., 2013Izel ACU, Crescêncio R, O’Sullivan FLA, Chagas EC, Boijink CL, Silva JI. Produção intensiva de tambaqui em tanques escavados com aeração (Circular técnica 39). Manaus: Embrapa Amazônia Ocidental; 2013.).

Fish health issues may be faced during any phase or farming system of tambaqui. Hilsdorf et al. (2022)Hilsdorf AWS, Hallerman E, Valladão GMR, Zaminhan-Hassemer M, Hashimoto DT, Dairiki JK, et al. The farming and husbandry of Colossoma macropomum: from Amazonian waters to sustainable production. Rev Aquacult 2022; 14(2): 993-1027. http://dx.doi.org/10.1111/raq.12638.
http://dx.doi.org/10.1111/raq.12638...
have reported parasitic infections, especially in the North region, and heterogenous growth as some of the bottlenecks in tambaqui farming. The main parasites reported for C. macropomum are Protozoa, Acanthocephala, Copepoda, Monogenea, Myxozoa and Crustacea species (Ferreira et al., 2018Ferreira JA Jr, Leonardo AS, Azevedo JPMVB, Rodrigues FR, Nascimento KA, Macêdo JTSA, et al. Surto de infecção por Piscinoodinium pillulare e Trichodina spp. em tambaquis (Colossoma macropomum), pirapitingas (Piaractus brachypomus) e tilápias (Oreochromis niloticus) no Distrito Federal. Acta Sci Vet 2018; 46(1): 293. ; Maciel et al., 2018Maciel PO, Garcia F, Chagas EC, Fujimoto RY, Tavares-Dias M. Trichodinidae in commercial fish in South America. Rev Fish Biol Fish 2018; 28(1): 33-56. http://dx.doi.org/10.1007/s11160-017-9490-1.
http://dx.doi.org/10.1007/s11160-017-949...
; Chagas et al., 2019Chagas EC, Aquino-Pereira SL, Benavides MV, Brandão FR, Monteiro PC, Maciel PO. Neoechinorhynchus buttnerae parasitic infection in tambaqui (Colossoma macropomum) on fish farms in the state of Amazonas. Bol Inst Pesca 2019; 45(2): e499. http://dx.doi.org/10.20950/1678-2305.2019.45.2.499.
http://dx.doi.org/10.20950/1678-2305.201...
; Fujimoto et al., 2019Fujimoto RY, Hide DMV, Paixão PEG, Abe HA, Dias JAR, Sousa NC, et al. Fauna parasitária e relação parasito-hospedeiro de tambaquis criados na região do baixo São Francisco, nordeste do Brasil. Arq Bras Med Vet Zootec 2019; 71(2): 563-570. http://dx.doi.org/10.1590/1678-4162-10306.
http://dx.doi.org/10.1590/1678-4162-1030...
; Andrade Porto et al., 2022Andrade Porto SM, Tavares-Dias M, Maciel PO, Castro LA. Crustáceos argulídeos e lerneídeos de peixes de água doce do Brasil. Cad Téc Vet Zootec 2022; 101: 109-153.). Among protozoans, disease outbreaks with high morbidity and mortality in the different culture phases have been associated to Piscinoodinium pillulare in the South-eastern and Western regions of Brazil (Martins et al., 2001Martins ML, Moraes JRE, Andrade PM, Schalch SHC, Moraes FR. Piscinoodinium pillulare (Schäperclaus, 1954) Lom, 1981 (Dinoflagellida) infection in cultivated freshwater fish from the northeast region of São Paulo State, Brazil: parasitological and pathological aspects. Braz J Biol 2001; 61(4): 639-644. http://dx.doi.org/10.1590/S1519-69842001000400013. PMid:12071320.
http://dx.doi.org/10.1590/S1519-69842001...
; Ferreira et al., 2018Ferreira JA Jr, Leonardo AS, Azevedo JPMVB, Rodrigues FR, Nascimento KA, Macêdo JTSA, et al. Surto de infecção por Piscinoodinium pillulare e Trichodina spp. em tambaquis (Colossoma macropomum), pirapitingas (Piaractus brachypomus) e tilápias (Oreochromis niloticus) no Distrito Federal. Acta Sci Vet 2018; 46(1): 293. ). Piscinoodinium pillulare is a mastigophore protozoal dinoflagellate with no host specificity, infecting host fish and causing integumentary petechiae, necrosis, and inflammation, further to hypertrophy and fusion of the secondary branchial lamellae, resulting in clinical signs consistent to asphyxia (Martins et al., 2015Martins ML, Cardoso L, Marchiori N, Pádua SB. Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Braz J Vet Parasitol 2015; 24(1): 1-20. http://dx.doi.org/10.1590/S1984-29612015013. PMid:25909248.
http://dx.doi.org/10.1590/S1984-29612015...
). Fish mortality rates of 40% to 90% have been reported due to P. pillulare infection (Martins et al., 2001Martins ML, Moraes JRE, Andrade PM, Schalch SHC, Moraes FR. Piscinoodinium pillulare (Schäperclaus, 1954) Lom, 1981 (Dinoflagellida) infection in cultivated freshwater fish from the northeast region of São Paulo State, Brazil: parasitological and pathological aspects. Braz J Biol 2001; 61(4): 639-644. http://dx.doi.org/10.1590/S1519-69842001000400013. PMid:12071320.
http://dx.doi.org/10.1590/S1519-69842001...
; Sant’Ana et al., 2012Sant’Ana FJF, Oliveira SL, Rabelo RE, Vulcani VAS, Silva SMG, Ferreira-Júnior JA. Surtos de infecção por Piscinoodinium pillulare e Henneguya spp. em pacus (Piaractus mesopotamicus) criados intensivamente no Sudoeste de Goiás. Pesq Vet Bras 2012; 32(2): 121-125. http://dx.doi.org/10.1590/S0100-736X2012000200005.
http://dx.doi.org/10.1590/S0100-736X2012...
). Another prevalent parasite in tambaqui farming is the acanthocephalan Neoechinorhynchus buttnerae, reported in farms in the states of Amazonas, Rondônia, Roraima and Maranhão (Chagas et al., 2015Chagas EC, Maciel PO, Aquino-Pereira SL. Infecções por acantocéfalos: um problema para a produção de peixes. In: Tavares-Dias M, Mariano WS, editors. Aquicultura no Brasil: novas perspectivas. Aspectos biológicos, fisiológicos e sanitários de organismos aquáticos. São Carlos: Pedro & João Editores; 2015. p. 305-328., 2019Chagas EC, Aquino-Pereira SL, Benavides MV, Brandão FR, Monteiro PC, Maciel PO. Neoechinorhynchus buttnerae parasitic infection in tambaqui (Colossoma macropomum) on fish farms in the state of Amazonas. Bol Inst Pesca 2019; 45(2): e499. http://dx.doi.org/10.20950/1678-2305.2019.45.2.499.
http://dx.doi.org/10.20950/1678-2305.201...
; Jerônimo et al., 2017Jerônimo GT, Pádua SB, Andrade Belo MA, Chagas EC, Taboga SR, Maciel PO, et al. Neoechinorhynchus buttnerae (Acanthocephala) infection in farmed Colossoma macropomum: a pathological approach. Aquaculture 2017; 469: 124-127. http://dx.doi.org/10.1016/j.aquaculture.2016.11.027.
http://dx.doi.org/10.1016/j.aquaculture....
; Lourenço et al., 2017Lourenço FS, Morey GAM, Pereira JN, Malta JCO. Occurrence of Neoechinorhynchus (Neoechinorhynchus) buttnerae Golvan, 1956 (Acantocephala: Neochinorhynchidae) in Colossoma macropomum (Cuvier, 1818) (Characiformes: Serrasalmidae) from a fish farm in the Brazilian Amazon. Folia Amaz 2017; 26(1): 1-8. http://dx.doi.org/10.24841/fa.v26i1.414.
http://dx.doi.org/10.24841/fa.v26i1.414...
; Pereira & Morey, 2018Pereira JN, Morey GAM. First record of Neoechinorhynchus buttnerae (Eoacantocephala, Neochinorhynchidae) on Colossoma macropomum (Characidae) in a fish farm in Roraima, Brazil. Acta Amazon 2018; 48(1): 42-45. http://dx.doi.org/10.1590/1809-4392201702411.
http://dx.doi.org/10.1590/1809-439220170...
). Their proboscis can pierce the gut wall of the host and cause stiffening and thickening of the mucous and muscular layers, resulting in intense inflammation and mucus production (Jerônimo et al., 2017Jerônimo GT, Pádua SB, Andrade Belo MA, Chagas EC, Taboga SR, Maciel PO, et al. Neoechinorhynchus buttnerae (Acanthocephala) infection in farmed Colossoma macropomum: a pathological approach. Aquaculture 2017; 469: 124-127. http://dx.doi.org/10.1016/j.aquaculture.2016.11.027.
http://dx.doi.org/10.1016/j.aquaculture....
; Matos et al., 2017Matos LV, Oliveira MIB, Gomes ALGALS, Silva GS. Morphological and histochemical changes associated with massive infection by Neoechinorhynchus buttnerae (Acanthocephala: Neoechinorhynchidae) in the farmed freshwater fish Colossoma macropomum Cuvier, 1818 from the Amazon State, Brazil. Parasitol Res 2017; 116(3): 1029-1037. http://dx.doi.org/10.1007/s00436-017-5384-3. PMid:28124738.
http://dx.doi.org/10.1007/s00436-017-538...
). Fish mortalities are not frequent; however, high infection rates can obstruct the gut lumen and jeopardize nutrient absorption and lead to weight loss (Chagas et al., 2015Chagas EC, Maciel PO, Aquino-Pereira SL. Infecções por acantocéfalos: um problema para a produção de peixes. In: Tavares-Dias M, Mariano WS, editors. Aquicultura no Brasil: novas perspectivas. Aspectos biológicos, fisiológicos e sanitários de organismos aquáticos. São Carlos: Pedro & João Editores; 2015. p. 305-328.; Silva-Gomes et al., 2017Silva-Gomes AL, Coelho-Filho JG, Viana-Silva W, Braga-Oliveira MI, Bernardino G, Costa JI. The impact of Neoechinorhynchus buttnerae (Golvan, 1956) (Eoacanthocephala: Neochinorhynchidae) outbreaks on productive and economic performance of the tambaqui Colossoma macropomum (Cuvier, 1818), reared in ponds. Lat Am J Aquat Res 2017; 45(2): 496-500. http://dx.doi.org/10.3856/vol45-issue2-fulltext-25.
http://dx.doi.org/10.3856/vol45-issue2-f...
).

In tambaqui farming, disease outbreaks are mostly related to intensification without due management practices (Valladão et al., 2018Valladão GMR, Gallani SU, Pilarski F. South American fish for continental aquaculture. Rev Aquacult 2018; 10(2): 351-369. http://dx.doi.org/10.1111/raq.12164.
http://dx.doi.org/10.1111/raq.12164...
). Intensive farming without good management practices can lead to unbalanced fish-pathogen-environment relationship and the fish becomes highly susceptible to diseases (Chagas et al., 2019Chagas EC, Aquino-Pereira SL, Benavides MV, Brandão FR, Monteiro PC, Maciel PO. Neoechinorhynchus buttnerae parasitic infection in tambaqui (Colossoma macropomum) on fish farms in the state of Amazonas. Bol Inst Pesca 2019; 45(2): e499. http://dx.doi.org/10.20950/1678-2305.2019.45.2.499.
http://dx.doi.org/10.20950/1678-2305.201...
; Costa et al., 2019Costa OTF, Dias LC, Malmann CSY, Ferreira CAL, Carmo IB, Wischneski AG, et al. The effects of stocking density on the hematology, plasma protein profile and immunoglobulin production of juvenile tambaqui (Colossoma macropomum) farmed in Brazil. Aquaculture 2019; 499: 260-268. http://dx.doi.org/10.1016/j.aquaculture.2018.09.040.
http://dx.doi.org/10.1016/j.aquaculture....
). It is estimated that Brazilian fish farms may suffer annual direct and indirect economic losses of USD 84 million due to the lack of good farm management practices according to Tavares-Dias & Martins (2017)Tavares-Dias M, Martins ML. An overall estimation of losses caused by diseases in the Brazilian fish farms. J Parasit Dis 2017; 41(4): 913-918. http://dx.doi.org/10.1007/s12639-017-0938-y. PMid:29114119.
http://dx.doi.org/10.1007/s12639-017-093...
.

In some countries, virtually all chemical products may be legally used to treat such a diversity of diseases, whereas in others, some restrictions may apply (Woynárovich & Van Anrooy, 2019Woynárovich A, Van Anrooy R. Field guide to the culture of tambaqui Colossoma macropomum, Cuvier, 1816. FAO Fish Aquac Tech Pap 2019; 624: 1-121.). In Brazil, veterinarian therapeutic products to be used in aquaculture are not widely available (Hilsdorf et al., 2022Hilsdorf AWS, Hallerman E, Valladão GMR, Zaminhan-Hassemer M, Hashimoto DT, Dairiki JK, et al. The farming and husbandry of Colossoma macropomum: from Amazonian waters to sustainable production. Rev Aquacult 2022; 14(2): 993-1027. http://dx.doi.org/10.1111/raq.12638.
http://dx.doi.org/10.1111/raq.12638...
). Thus, several studies have been conducted testing synthetic products available in the market, as well as the investigation of active ingredients of medicinal plants for therapeutic and prophylactic treatments in tambaqui, to encourage the authorities to approve new products.

With the growth of aquaculture in Brazil and the description and reporting of new diseases and their region of occurrence, studies that expand the epidemiological characterization of diseases in tambaqui farming are crucial. So is the compilation of scientific information on treatment of such diseases. These would contribute to a better understanding of the research done in this area and provide the necessary guidance towards the correct means of treatment and prevention. On this point of view, the aims of the present study were to report the occurrence of Piscinoodinium pillulare and Neoechinorhynchus buttnerae in tambaqui farms in the state of Tocantins (TO), Brazil, and suggest the main treatments available to control such parasitic infection in the host.

Materials and Methods

A technical visit was conducted at a tambaqui farm in Novo Acordo, TO, Brazil, due to possible sanitary issues at the property. The farmer reported fish low weight gain and reduced appetite, fish swimming near the water surface and swelling of the fish bottom lips to help breathing, and changes in the fish skin coloration.

Fish were farmed in one 1,000 m2 pond stocked at a density of 3 fish/m2, in a semi-intensive, single phase monoculture system. The fish had been stocked for one year and their measurements have not been taken throughout. In total, the farm had seven earthen ponds (total of 8,500 m2) stocked with other fish species as well, i.e., Arapaima gigas (pirarucu) and Brycon amazonicus (matrinxã), in semi-intensive system. The fish farm had been in operation for eight years, mainly for their subsistence and the ponds had never been drained or dried for disinfection. In the tambaqui pond, the water was highly transparent, with excess organic matter in the bottom and the water outlet was through the surface.

Twenty-one tambaqui fish were sampled from the pond using fishing nets and transferred to plastic bags with 1/3 water and 2/3 oxygen and transported to the Fish Health and Disease Laboratory, Embrapa Fisheries and Aquaculture, Palmas, TO. Fish were anesthetised (Roubach et al., 2005Roubach R, Gomes LC, Fonseca FAL, Val AL. Eugenol as an efficacious anaesthetic for tambaqui, Colossoma macropomum (Cuvier). Aquacult Res 2005; 36(11): 1056-1061. http://dx.doi.org/10.1111/j.1365-2109.2005.01319.x.
http://dx.doi.org/10.1111/j.1365-2109.20...
) and killed by medullar section to proceed to measurements, necropsy, and sampling of biological material for parasitological analysis according to Eiras et al. (2006)Eiras JC, Takemoto RM, Pavanelli GC. Métodos de estudo e técnicas laboratoriais em parasitologia de peixes. Maringá: Eduem; 2006.. Fish were macroscopically examined for physical alterations and skin lesions. Mucus was collected from head to tail from the fish body surface with a glass slide and the wet mount observed under a light microscope. The branchial arcs were excised, placed in 4% buffered formalin, and vigorously shaken to detach the parasites and fixed for analysis. Fish abdominal cavity was opened, and organs removed and placed on Petri dishes to be analysed under a dissecting microscope. Subsequently, the intestine was separately fixed in 4% buffered formalin for later qualitative and quantitative analysis of the parasites. Fish management was according to the ethics of animal use by the Brazilian Society of Laboratory Animal Science (COBEA).

Sampling, fixing, identification and counting of the parasites were done according to methods described by-Eiras et al. (2006)Eiras JC, Takemoto RM, Pavanelli GC. Métodos de estudo e técnicas laboratoriais em parasitologia de peixes. Maringá: Eduem; 2006. and Thatcher (2006)Thatcher VE. Amazon fish parasites. Moscow: Sofia; 2006.. For the gills, three 1-mL sub-samples were taken from the fixated material to count the protozoans in a Sedgewick-Rafter chamber, according to Maciel et al. (2018)Maciel PO, Garcia F, Chagas EC, Fujimoto RY, Tavares-Dias M. Trichodinidae in commercial fish in South America. Rev Fish Biol Fish 2018; 28(1): 33-56. http://dx.doi.org/10.1007/s11160-017-9490-1.
http://dx.doi.org/10.1007/s11160-017-949...
. In the fish mucus, the protozoan P. pillulare were counted per score, according to Rach et al. (2000)Rach JJ, Gaikowski MP, Ramsay RT. Efficacy of hydrogen peroxide to control parasitic infestations on hatchery-reared fish. J Aquat Anim Health 2000; 12(4): 267-273. http://dx.doi.org/10.1577/1548-8667(2000)012<0267:EOHPTC>2.0.CO;2.
http://dx.doi.org/10.1577/1548-8667(2000...
. Acanthocephan parasites were also quantified. The parasitic prevalence index (P), mean intensity (MI), and mean abundance (MA) were calculated according to Bush et al. (1997)Bush AO, Lafferty KD, Lotz JM, Shostak AW. Parasitology meets ecology on its own terms: margolis et al. revisited. J Parasitol 1997; 83(4): 575-583. http://dx.doi.org/10.2307/3284227. PMid:9267395.
http://dx.doi.org/10.2307/3284227...
.

Results and Discussion

Mean body weight ± s.d. and mean standard length ± s.d. of the tambaqui sampled at the farm were 205.9 ± 76.5 g and 22.0 ± 2.4 cm, respectively, which could be considered as initial grow-out phase. However, fish had already been stocked in the pond for 12 months, meaning that the fish weight was much below the expected for the age. In this type of system, it becomes difficult to control pathogenic agents from entering the ponds together with the new batches of fish. The lack of disinfection procedures between farming cycles is a serious management issue that can jeopardize the entire production.

Parasitic prevalence in the sampled fish varied in dependence on the parasites. Piscinoodinium pillulare was observed together with N. buttnerae. Infection by P. pillulare was the highest in the sampled fish (Table 1), with mean intensity values above those reported for tambaqui farmed in cages in Amapá (Santos et al., 2013aSantos EF, Tavares-Dias M, Pinheiro DA, Neves LR, Marinho RGB, Dias MKR. Fauna parasitária de tambaqui Colossoma macropomum (Characidae) cultivado em tanque-rede no estado do Amapá, Amazônia oriental. Acta Amaz 2013a; 43(1): 105-111. http://dx.doi.org/10.1590/S0044-59672013000100013.
http://dx.doi.org/10.1590/S0044-59672013...
) or in earthen ponds in Venezuela (Dezon De Fogel et al., 2004Dezon De Fogel DE, Zambrano JLF, Gonzalez I. Parasitism in cultivated Colossoma macropomum (Pisces: Characidae), due to the protozoans Ichthyophthirius multifilis (Fouquet) and Piscinoodinium pillulare (Schäperclaus). Saber (Cumaná) 2004; 16(1): 3-8.). Parasitic co-infection may be common in some disease outbreaks, but usually only one pathogenic agent is more strongly related to the clinical signs and fish health status. Ferreira et al. (2018)Ferreira JA Jr, Leonardo AS, Azevedo JPMVB, Rodrigues FR, Nascimento KA, Macêdo JTSA, et al. Surto de infecção por Piscinoodinium pillulare e Trichodina spp. em tambaquis (Colossoma macropomum), pirapitingas (Piaractus brachypomus) e tilápias (Oreochromis niloticus) no Distrito Federal. Acta Sci Vet 2018; 46(1): 293. reported co-infection by P. pillulare and Trichodina spp. in C. macropomum farmed in the Federal District, Brazil. Co-infection by the protozoan P. pillulare and Ichthyophthirius multifiliis was reported by Dezon De Fogel et al. (2004)Dezon De Fogel DE, Zambrano JLF, Gonzalez I. Parasitism in cultivated Colossoma macropomum (Pisces: Characidae), due to the protozoans Ichthyophthirius multifilis (Fouquet) and Piscinoodinium pillulare (Schäperclaus). Saber (Cumaná) 2004; 16(1): 3-8. in tambaqui in Venezuela. In all such cases, P. pillulare was the prevailing infection and reported as the main cause of the outbreak, fish morbidity and mortality, which corroborates with the findings of the present study.

Table 1
Parasitological indices in Colossoma macropomum of a fish farm in the municipality of Novo Acordo, State of Tocantins.

The dinoflagellate P. pillulare can be found on the fish body surface and gills, as they are naturally present in aquatic systems, without causing any harm when the system is in equilibrium (Martins et al., 2015Martins ML, Cardoso L, Marchiori N, Pádua SB. Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Braz J Vet Parasitol 2015; 24(1): 1-20. http://dx.doi.org/10.1590/S1984-29612015013. PMid:25909248.
http://dx.doi.org/10.1590/S1984-29612015...
). Accordingly, Fujimoto et al. (2019)Fujimoto RY, Hide DMV, Paixão PEG, Abe HA, Dias JAR, Sousa NC, et al. Fauna parasitária e relação parasito-hospedeiro de tambaquis criados na região do baixo São Francisco, nordeste do Brasil. Arq Bras Med Vet Zootec 2019; 71(2): 563-570. http://dx.doi.org/10.1590/1678-4162-10306.
http://dx.doi.org/10.1590/1678-4162-1030...
reported low prevalence of P. pillulare in C. macropomum farmed in earthen ponds. Santos et al. (2013a)Santos EF, Tavares-Dias M, Pinheiro DA, Neves LR, Marinho RGB, Dias MKR. Fauna parasitária de tambaqui Colossoma macropomum (Characidae) cultivado em tanque-rede no estado do Amapá, Amazônia oriental. Acta Amaz 2013a; 43(1): 105-111. http://dx.doi.org/10.1590/S0044-59672013000100013.
http://dx.doi.org/10.1590/S0044-59672013...
reported high infection levels of P. pillulare in C. macropomum reared in cages, but without fish presenting any clinical signs. These differences may be due to differences of environments. However, in the present study, tambaqui skin colour was greenish-brown and darkened gills, as reported by Arbildo-Ortiz et al. (2020)Arbildo-Ortiz H, Alvez-Robledo J, Guardia CC, Souza AKS. Primer registro de infestación de Piscinoodinium pillulare (Dinoflagellida) en juveniles de Colossoma macropomum (Characiformes: Serrasalmidae) en cultivo semi-intensivo en Loreto, Perú. Rev Investig Vet Peru 2020; 31(3): e16662. http://dx.doi.org/10.15381/rivep.v31i3.16662.
http://dx.doi.org/10.15381/rivep.v31i3.1...
, who additionally reported skin necrosis and petechiae in C. macropomum. Furthermore, clinical signs of dysfunctional breathing, such as swimming near the water surface and swollen bottom lips were observed. Such clinical signs had been also previously described in P. pillulare infection in other fish species (Martins et al., 2001Martins ML, Moraes JRE, Andrade PM, Schalch SHC, Moraes FR. Piscinoodinium pillulare (Schäperclaus, 1954) Lom, 1981 (Dinoflagellida) infection in cultivated freshwater fish from the northeast region of São Paulo State, Brazil: parasitological and pathological aspects. Braz J Biol 2001; 61(4): 639-644. http://dx.doi.org/10.1590/S1519-69842001000400013. PMid:12071320.
http://dx.doi.org/10.1590/S1519-69842001...
, 2015Martins ML, Cardoso L, Marchiori N, Pádua SB. Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Braz J Vet Parasitol 2015; 24(1): 1-20. http://dx.doi.org/10.1590/S1984-29612015013. PMid:25909248.
http://dx.doi.org/10.1590/S1984-29612015...
; Sant'Ana et al., 2012Sant’Ana FJF, Oliveira SL, Rabelo RE, Vulcani VAS, Silva SMG, Ferreira-Júnior JA. Surtos de infecção por Piscinoodinium pillulare e Henneguya spp. em pacus (Piaractus mesopotamicus) criados intensivamente no Sudoeste de Goiás. Pesq Vet Bras 2012; 32(2): 121-125. http://dx.doi.org/10.1590/S0100-736X2012000200005.
http://dx.doi.org/10.1590/S0100-736X2012...
).

The rapid increase in the number of P. pillulare in farming conditions is promoted by low host specificity (Martins et al., 2015Martins ML, Cardoso L, Marchiori N, Pádua SB. Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Braz J Vet Parasitol 2015; 24(1): 1-20. http://dx.doi.org/10.1590/S1984-29612015013. PMid:25909248.
http://dx.doi.org/10.1590/S1984-29612015...
), as well as poor management practices, such as high stocking densities, poor water quality and inadequate nutrition (Martins et al., 2001Martins ML, Moraes JRE, Andrade PM, Schalch SHC, Moraes FR. Piscinoodinium pillulare (Schäperclaus, 1954) Lom, 1981 (Dinoflagellida) infection in cultivated freshwater fish from the northeast region of São Paulo State, Brazil: parasitological and pathological aspects. Braz J Biol 2001; 61(4): 639-644. http://dx.doi.org/10.1590/S1519-69842001000400013. PMid:12071320.
http://dx.doi.org/10.1590/S1519-69842001...
, 2015Martins ML, Cardoso L, Marchiori N, Pádua SB. Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Braz J Vet Parasitol 2015; 24(1): 1-20. http://dx.doi.org/10.1590/S1984-29612015013. PMid:25909248.
http://dx.doi.org/10.1590/S1984-29612015...
; Sant'Ana et al., 2012Sant’Ana FJF, Oliveira SL, Rabelo RE, Vulcani VAS, Silva SMG, Ferreira-Júnior JA. Surtos de infecção por Piscinoodinium pillulare e Henneguya spp. em pacus (Piaractus mesopotamicus) criados intensivamente no Sudoeste de Goiás. Pesq Vet Bras 2012; 32(2): 121-125. http://dx.doi.org/10.1590/S0100-736X2012000200005.
http://dx.doi.org/10.1590/S0100-736X2012...
). In this study, fish stocking density was above the recommendation, high transparency in pond water and excess organic matter in the tank bottom, no draining and disinfection of the pond between cycles, which all may have contributed to the outbreak of P. pillulare infection. Therefore, risk factors associated to this parasite are directly related to both poor fish growth and water quality (Fujimoto et al., 2019Fujimoto RY, Hide DMV, Paixão PEG, Abe HA, Dias JAR, Sousa NC, et al. Fauna parasitária e relação parasito-hospedeiro de tambaquis criados na região do baixo São Francisco, nordeste do Brasil. Arq Bras Med Vet Zootec 2019; 71(2): 563-570. http://dx.doi.org/10.1590/1678-4162-10306.
http://dx.doi.org/10.1590/1678-4162-1030...
). Unbalance in those variables and their impact on the parasite-host-environment relationship may lead to stress, compromised immune response and fish highly susceptible to such parasitic infection (Santos et al., 2013aSantos EF, Tavares-Dias M, Pinheiro DA, Neves LR, Marinho RGB, Dias MKR. Fauna parasitária de tambaqui Colossoma macropomum (Characidae) cultivado em tanque-rede no estado do Amapá, Amazônia oriental. Acta Amaz 2013a; 43(1): 105-111. http://dx.doi.org/10.1590/S0044-59672013000100013.
http://dx.doi.org/10.1590/S0044-59672013...
). Accordingly, exceeding the pond carrying capacity will result in poor water quality, impaired in fish growth, increased contact, leading to disease outbreak (Baldwin, 2010Baldwin L. The effects of stocking density on fish welfare. Plym Stud Sci 2010; 4(1): 372-383.; Associação Brasileira da Piscicultura - PeixeBR, 2021Associação Brasileira da Piscicultura - PeixeBR. Guia Biosseguridade PeixeBR [online]. 2021 [cited 2022 Aug 12]. Available form: https://www.peixebr.com.br/anuario2022
https://www.peixebr.com.br/anuario2022...
).

The acanthocephalan N. buttnerae were observed in the gut of tambaqui farmed in the state of Tocantins at 100% prevalence, intensity of 19 to 234 parasites per fish, at a total of 1,080 individuals (Table 1). Localized increase in the diameter of the fish intestinal loops was an external sign of the presence of those parasites in the gut. In two of the sampled fish, one and two acanthocephalans were found in the fish stomach, but it was most probably an unusual migration of the parasite. In this study, the mean intensity of N. buttnerae was lower than previously reported in tambaqui farmed in the states of Roraima: 188 to 388 (Pereira & Morey, 2018Pereira JN, Morey GAM. First record of Neoechinorhynchus buttnerae (Eoacantocephala, Neochinorhynchidae) on Colossoma macropomum (Characidae) in a fish farm in Roraima, Brazil. Acta Amazon 2018; 48(1): 42-45. http://dx.doi.org/10.1590/1809-4392201702411.
http://dx.doi.org/10.1590/1809-439220170...
) and Amazonas: 31 to 406 (Malta et al., 2001Malta JCO, Gomes AL, Andrade SMS, Varella AMB. Infestações maciças por acantocéfalos, Neoechinorhynchus buttnerae Golvan, 1956, (Eoacanthocephala: Neoechinorhynchidae) em tambaquis jovens, Colossoma macropomum (Cuvier, 1818) cultivados na Amazônia Central. Acta Amaz 2001; 31(1): 133-143. http://dx.doi.org/10.1590/1809-43922001311143.
http://dx.doi.org/10.1590/1809-439220013...
); 81 to 708 (Matos et al., 2017Matos LV, Oliveira MIB, Gomes ALGALS, Silva GS. Morphological and histochemical changes associated with massive infection by Neoechinorhynchus buttnerae (Acanthocephala: Neoechinorhynchidae) in the farmed freshwater fish Colossoma macropomum Cuvier, 1818 from the Amazon State, Brazil. Parasitol Res 2017; 116(3): 1029-1037. http://dx.doi.org/10.1007/s00436-017-5384-3. PMid:28124738.
http://dx.doi.org/10.1007/s00436-017-538...
); 15 to 720 (Silva-Gomes et al., 2017Silva-Gomes AL, Coelho-Filho JG, Viana-Silva W, Braga-Oliveira MI, Bernardino G, Costa JI. The impact of Neoechinorhynchus buttnerae (Golvan, 1956) (Eoacanthocephala: Neochinorhynchidae) outbreaks on productive and economic performance of the tambaqui Colossoma macropomum (Cuvier, 1818), reared in ponds. Lat Am J Aquat Res 2017; 45(2): 496-500. http://dx.doi.org/10.3856/vol45-issue2-fulltext-25.
http://dx.doi.org/10.3856/vol45-issue2-f...
), 107 to 921 (Lourenço et al., 2017Lourenço FS, Morey GAM, Pereira JN, Malta JCO. Occurrence of Neoechinorhynchus (Neoechinorhynchus) buttnerae Golvan, 1956 (Acantocephala: Neochinorhynchidae) in Colossoma macropomum (Cuvier, 1818) (Characiformes: Serrasalmidae) from a fish farm in the Brazilian Amazon. Folia Amaz 2017; 26(1): 1-8. http://dx.doi.org/10.24841/fa.v26i1.414.
http://dx.doi.org/10.24841/fa.v26i1.414...
); 54 to 931 and 81 to 1.219 (Chagas et al., 2019Chagas EC, Aquino-Pereira SL, Benavides MV, Brandão FR, Monteiro PC, Maciel PO. Neoechinorhynchus buttnerae parasitic infection in tambaqui (Colossoma macropomum) on fish farms in the state of Amazonas. Bol Inst Pesca 2019; 45(2): e499. http://dx.doi.org/10.20950/1678-2305.2019.45.2.499.
http://dx.doi.org/10.20950/1678-2305.201...
). Such variation in the parasitic index may be due to different conditions adopted in the farms and stages of the culture cycle when the fish were sampled. Since no draining and disinfection of the pond was practiced in the farm, it is not possible to trace back the origin of the infection, if infected fish were brought into the farm or if they got infected because the pond was already contaminated from previous batches. Incompatible stocking density, i.e., intensification, as well as no adoption of good farm management practices, e.g., draining, disinfection of ponds between cycles, are favorable conditions to the growth of acanthocephalans on intermediate hosts and on newly stocked fish in the following cycle.

Acanthocephalan parasites are heteroxenous, dioecious, and reproduce inside the fish digestive system. Their fertilized eggs are released in the water together with the fish feces, and the eggs are eaten by arthropods, which are eaten by the fish, closing the life cycle that involves an arthropod as intermediate host and a vertebrate as a definitive host (Santos et al., 2013bSantos CP, Borges JN, Fernandes ES, Santos EGN. Acanthocephala. In: Pavanelli C, Takemoto RM, Eiras JC, editors. Parasitologia de peixes de água doce do Brasil. Maringá: Eduem; 2013b. p. 333-352.). The ostracod Cypridopsis vidua is the intermediate host for N. buttnerae, inside which the parasite grows for 29 days (Lourenço et al., 2017Lourenço FS, Morey GAM, Pereira JN, Malta JCO. Occurrence of Neoechinorhynchus (Neoechinorhynchus) buttnerae Golvan, 1956 (Acantocephala: Neochinorhynchidae) in Colossoma macropomum (Cuvier, 1818) (Characiformes: Serrasalmidae) from a fish farm in the Brazilian Amazon. Folia Amaz 2017; 26(1): 1-8. http://dx.doi.org/10.24841/fa.v26i1.414.
http://dx.doi.org/10.24841/fa.v26i1.414...
; Chagas et al., 2019Chagas EC, Aquino-Pereira SL, Benavides MV, Brandão FR, Monteiro PC, Maciel PO. Neoechinorhynchus buttnerae parasitic infection in tambaqui (Colossoma macropomum) on fish farms in the state of Amazonas. Bol Inst Pesca 2019; 45(2): e499. http://dx.doi.org/10.20950/1678-2305.2019.45.2.499.
http://dx.doi.org/10.20950/1678-2305.201...
). The acanthocephalan N. buttnerae causes severe pathogenicity in tambaqui (Jerônimo et al., 2017Jerônimo GT, Pádua SB, Andrade Belo MA, Chagas EC, Taboga SR, Maciel PO, et al. Neoechinorhynchus buttnerae (Acanthocephala) infection in farmed Colossoma macropomum: a pathological approach. Aquaculture 2017; 469: 124-127. http://dx.doi.org/10.1016/j.aquaculture.2016.11.027.
http://dx.doi.org/10.1016/j.aquaculture....
; Matos et al., 2017Matos LV, Oliveira MIB, Gomes ALGALS, Silva GS. Morphological and histochemical changes associated with massive infection by Neoechinorhynchus buttnerae (Acanthocephala: Neoechinorhynchidae) in the farmed freshwater fish Colossoma macropomum Cuvier, 1818 from the Amazon State, Brazil. Parasitol Res 2017; 116(3): 1029-1037. http://dx.doi.org/10.1007/s00436-017-5384-3. PMid:28124738.
http://dx.doi.org/10.1007/s00436-017-538...
). An antiparasitic strategy to control of this endoparasite should the elimination of the intermediate host in environment.

So far, the distribution of N. buttnerae in tambaqui had been restricted to the states of Amazonas (Malta et al., 2001Malta JCO, Gomes AL, Andrade SMS, Varella AMB. Infestações maciças por acantocéfalos, Neoechinorhynchus buttnerae Golvan, 1956, (Eoacanthocephala: Neoechinorhynchidae) em tambaquis jovens, Colossoma macropomum (Cuvier, 1818) cultivados na Amazônia Central. Acta Amaz 2001; 31(1): 133-143. http://dx.doi.org/10.1590/1809-43922001311143.
http://dx.doi.org/10.1590/1809-439220013...
; Jerônimo et al., 2017Jerônimo GT, Pádua SB, Andrade Belo MA, Chagas EC, Taboga SR, Maciel PO, et al. Neoechinorhynchus buttnerae (Acanthocephala) infection in farmed Colossoma macropomum: a pathological approach. Aquaculture 2017; 469: 124-127. http://dx.doi.org/10.1016/j.aquaculture.2016.11.027.
http://dx.doi.org/10.1016/j.aquaculture....
; Lourenço et al., 2017Lourenço FS, Morey GAM, Pereira JN, Malta JCO. Occurrence of Neoechinorhynchus (Neoechinorhynchus) buttnerae Golvan, 1956 (Acantocephala: Neochinorhynchidae) in Colossoma macropomum (Cuvier, 1818) (Characiformes: Serrasalmidae) from a fish farm in the Brazilian Amazon. Folia Amaz 2017; 26(1): 1-8. http://dx.doi.org/10.24841/fa.v26i1.414.
http://dx.doi.org/10.24841/fa.v26i1.414...
; Chagas et al., 2019Chagas EC, Aquino-Pereira SL, Benavides MV, Brandão FR, Monteiro PC, Maciel PO. Neoechinorhynchus buttnerae parasitic infection in tambaqui (Colossoma macropomum) on fish farms in the state of Amazonas. Bol Inst Pesca 2019; 45(2): e499. http://dx.doi.org/10.20950/1678-2305.2019.45.2.499.
http://dx.doi.org/10.20950/1678-2305.201...
; Valladão et al., 2020Valladão GMR, Gallani SU, Jerônimo GT, de Seixas AT. Challenges in the control of acanthocephalosis in aquaculture: special emphasis on Neoechinorhynchus buttnerae. Rev Aquacult 2020; 12: 1360-1372.), Rondônia (Oliveira et al., 2015Oliveira SRKS, Bezera MVP, Belo MMA. Study of the endoparasites in tambaquis, Colossoma macropomum, from fish farms of Jamari Valley, State of Rondônia. Enc Bios 2015; 11(21): 1026-1041.; Jerônimo et al., 2017Jerônimo GT, Pádua SB, Andrade Belo MA, Chagas EC, Taboga SR, Maciel PO, et al. Neoechinorhynchus buttnerae (Acanthocephala) infection in farmed Colossoma macropomum: a pathological approach. Aquaculture 2017; 469: 124-127. http://dx.doi.org/10.1016/j.aquaculture.2016.11.027.
http://dx.doi.org/10.1016/j.aquaculture....
), Roraima (Pereira & Morey, 2018Pereira JN, Morey GAM. First record of Neoechinorhynchus buttnerae (Eoacantocephala, Neochinorhynchidae) on Colossoma macropomum (Characidae) in a fish farm in Roraima, Brazil. Acta Amazon 2018; 48(1): 42-45. http://dx.doi.org/10.1590/1809-4392201702411.
http://dx.doi.org/10.1590/1809-439220170...
) and Maranhão (Chagas et al., 2015Chagas EC, Maciel PO, Aquino-Pereira SL. Infecções por acantocéfalos: um problema para a produção de peixes. In: Tavares-Dias M, Mariano WS, editors. Aquicultura no Brasil: novas perspectivas. Aspectos biológicos, fisiológicos e sanitários de organismos aquáticos. São Carlos: Pedro & João Editores; 2015. p. 305-328.), although tambaqui is farmed throughout the North, Northeast, and Central-West regions in Brazil (Associação Brasileira da Piscicultura - PeixeBR, 2022Associação Brasileira da Piscicultura - PeixeBR. Anuário Peixe BR de piscicultura 2022 [online]. 2022 [cited 2022 Aug 20]. Available form: https://www.peixebr.com.br/anuario2022
https://www.peixebr.com.br/anuario2022...
). In the state of Amapá N. buttnerae infection has been reported in the hybrids tambatinga (♀C. macropomum x ♂P. brachypomus) (Dias et al., 2015Dias MKR, Neves LR, Marinho RGB, Pinheiro DA, Tavares-Dias M. Parasitismo em tambatinga (Colossoma macropomum x Piaractus brachypomus, Characidae) cultivados na Amazônia, Brasil. Acta Amaz 2015; 45(2): 231-238. http://dx.doi.org/10.1590/1809-4392201400974.
http://dx.doi.org/10.1590/1809-439220140...
) and tambacu (♀C. macropomum x ♂P. mesopotamicus) (Silva et al., 2013Silva RM, Tavares-Dias M, Dias MWR, Dias MKR, Marinho RGB. Parasitic fauna in hybrid tambacu from fish farms. Pesqui Agropecu Bras 2013; 48(8): 1049-1057. http://dx.doi.org/10.1590/S0100-204X2013000800034.
http://dx.doi.org/10.1590/S0100-204X2013...
). The present study is the first to report the occurrence of N. buttnerae in the state of Tocantins, increasing its distribution area to another state, which must be serve as an alert to the spreading of the disease across the tambaqui farms. Henceforth, sanitary inspection agencies and local farmers should be vigilant to the interstate trading of tambaqui fingerlings, which may be a possible source of disease spread.

Although the main signs in fish reported in this study were related to P. pillulare infection, weight loss correlates to N. buttnerae infection. Fish growth performance parameters such as weight gain, final biomass, and yield per farmed area in Amazonas had a reduction of more than 200% in fish infected by those acanthocephalans, directly affecting the gross profit of the farms (Silva-Gomes et al., 2017Silva-Gomes AL, Coelho-Filho JG, Viana-Silva W, Braga-Oliveira MI, Bernardino G, Costa JI. The impact of Neoechinorhynchus buttnerae (Golvan, 1956) (Eoacanthocephala: Neochinorhynchidae) outbreaks on productive and economic performance of the tambaqui Colossoma macropomum (Cuvier, 1818), reared in ponds. Lat Am J Aquat Res 2017; 45(2): 496-500. http://dx.doi.org/10.3856/vol45-issue2-fulltext-25.
http://dx.doi.org/10.3856/vol45-issue2-f...
). Therefore, even if the acanthocephalan infection does not cause fish mortality, performance losses must be considered, and prevention and treatment are fundamental.

The official list of authorized drugs to be used in aquaculture is not sufficient to cater to the needs of the different farming systems and fish species farmed in Brazil, thus, to control diseases caused by P. pillulare and N. buttnerae in tambaqui is challenging. In face of such situation, indiscriminate use of different chemicals, such as benzimidazoles, copper sulphate, potassium permanganate, formalin, among others, has increased in the desperate attempt to control the problem. Nevertheless, the use of such chemicals without knowing the adequate dose or period of administration, may lead to pathogen resistance, and even render the treatments inefficient once they become available. Furthermore, it can lead to immune suppression in the fish, environmental pollution, and food safety issue, as chemical residues may deposit in the fish flesh.

Studies have been conducted with some commercially available synthetic products, as well as with bioactive ingredients from medicinal plants, to stablish protocols to treat and control those parasitic infections by P. pillulare and N. buttnerae in tambaqui, and results are presented in Tables 2 and 3. The use of chemical treatments to control parasitic infections in farmed fish is a strategy in many countries, but these products are in general toxic to the host fish (Castro et al., 2021Castro LA, Andrade-Porto SM, Oliveira RG, Batista YL, Silva FMA, Oliveira CPF, et al. Antiparasitic efficacy of dietary administration of trichlorfon (Masoten®) in the control of Neoechinorhynchus buttnerae (Neochinorhynchidae) in Colossoma macropomum (Serrasalmidae). Aquacult Int 2021; 29(6): 2477-2488. http://dx.doi.org/10.1007/s10499-021-00763-w.
http://dx.doi.org/10.1007/s10499-021-007...
), thus essential oils have been used as antiparasitic strategy. Neoechinorhynchus buttnerae has detrimental consequences for the health of tambaqui (Jerônimo et al., 2017Jerônimo GT, Pádua SB, Andrade Belo MA, Chagas EC, Taboga SR, Maciel PO, et al. Neoechinorhynchus buttnerae (Acanthocephala) infection in farmed Colossoma macropomum: a pathological approach. Aquaculture 2017; 469: 124-127. http://dx.doi.org/10.1016/j.aquaculture.2016.11.027.
http://dx.doi.org/10.1016/j.aquaculture....
; Lourenço et al., 2017Lourenço FS, Morey GAM, Pereira JN, Malta JCO. Occurrence of Neoechinorhynchus (Neoechinorhynchus) buttnerae Golvan, 1956 (Acantocephala: Neochinorhynchidae) in Colossoma macropomum (Cuvier, 1818) (Characiformes: Serrasalmidae) from a fish farm in the Brazilian Amazon. Folia Amaz 2017; 26(1): 1-8. http://dx.doi.org/10.24841/fa.v26i1.414.
http://dx.doi.org/10.24841/fa.v26i1.414...
; Matos et al., 2017Matos LV, Oliveira MIB, Gomes ALGALS, Silva GS. Morphological and histochemical changes associated with massive infection by Neoechinorhynchus buttnerae (Acanthocephala: Neoechinorhynchidae) in the farmed freshwater fish Colossoma macropomum Cuvier, 1818 from the Amazon State, Brazil. Parasitol Res 2017; 116(3): 1029-1037. http://dx.doi.org/10.1007/s00436-017-5384-3. PMid:28124738.
http://dx.doi.org/10.1007/s00436-017-538...
); however, control and treatment have been limited due to a lack of therapeutic products. Although the use of products extracted from plants can mean alternatives for fish diseases prevention and treatment, their use has been also limited by the efficacy and toxicity to fish. In addition, it is important to note that some results were effectives, however, such studies have not been yet validated in the field, where environmental and farming conditions may affect the results and even oppose those laboratory findings. Furthermore, other therapeutic strategies need to be tested to offer efficient and safe treatment options for these parasitic infections affecting tambaqui. Despite the promising results cited in present study, further studies are needed to assess the pharmacokinetics and pharmacodynamics of these chemotherapeutic and herbal products, in addition to the impact of the costs of the implementing treatments for the cultivation of tambaqui.

Table 2
Therapeutic management strategies to control and treatment against infections by Piscinoodinium pillulare in Colossoma macropomum.
Table 3
Therapeutic management strategies to control and treatment against infections by Neoechinorhynchus buttnerae in Colossoma macropomum.

Conclusions

This study was the first report of Piscinoodinium pillulare and Neoechinorhynchus buttnerae parasitic infection for tambaqui in the state of Tocantins, Brazil, emphasising the need to adopt good farm management and sanitary practices. Such practices include adopting recommended stocking densities, redesigning pond water outlet to discharge water from the bottom, monitoring water quality, adopting fish grading for growth and sanitary management, draining and disinfecting ponds between cycles - including liming and use of fertilizer to reduce organic matter load, control parasites and intermediate hosts of the pond bottom, practicing farm biosecurity - adopt a pond to quarantine the fish fingerling or juveniles before going into production, and adopt polyphase system - reducing the time spent by a batch of fish in the same pond. In addition to that, disinfection system for the farm materials and tools should be adopted to avoid the disease spreading between ponds or even between farms in case those materials are shared.

Acknowledgements

To the BRS Aqua Project, a partnership between BNDES, FEA and Embrapa, with the contribution of resources from BNDES, SAP/MAPA, counterpart from Embrapa and support from CNPq. Tavares-Dias, M. and Chagas, E.C. were supported by a research fellowship from the Conselho Nacional de Pesquisa e Desenvolvimento Tecnológico (CNPq, Brazil) (Grant 303013/2015-0 and 315771/2020-8, respectively). Ethics declaration This study was developed in accordance with the principles adopted by the Brazilian College of Animal Experimentation (COBEA) and with authorization from the Ethics Committee in the Use of Animals of Embrapa Amapá (Protocol No 014- CEUA/CPAFAP).

  • How to cite: Maciel-Honda PO, Sousa Neto EM, Costa-Fernandes TO, Jesus FHR, Chagas EC, Tavares-Dias M. First record of Neoechinorhynchus buttnerae and Piscinoodinium pillulare infection in Colossoma macropomum in the state of Tocantins, Brazil. Braz J Vet Parasitol 2023; 32(1): e013622. https://doi.org/10.1590/S1984-29612023001

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Publication Dates

  • Publication in this collection
    13 Jan 2023
  • Date of issue
    2023

History

  • Received
    23 Sept 2022
  • Accepted
    01 Nov 2022
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