Contágio intradomiciliar e status vacinal entre comunicantes de portatores do vírus da hepatite B / House hold contagion and vaccination status among communicants of hepatitis B virus carriers

Objetivo: Avaliar a cobertura da vacina contra hepatite B e a frequência da infecção em comunicantes de portadores do Vírus da Hepatite B vinte anos após a implementação da vacina na cidade de Belém, Pará, Brasil. Método: Estudo descritivo quantitativo, desenvolvido entre 2016 e 2018. Foram realizadas visitas domiciliares aos portadores do vírus, notificados por meio da busca de comunicantes, com orientações sobre a pesquisa, preenchimento e assinatura de formulários, coleta de amostras para testes sorológicos de hepatite B (HBsAg, anti-HBc total, anti-HBs) por técnica imunoenzimática. Resultados: Na população analisada 53,5% são do sexo masculino, com média de idade de 9,4 anos (entre 4 meses a 19 anos com mediana de 10 anos). Não foram detectados portadores de HBsAg reagente; anti-HBc isolado total foi detectado em 2,1%; 4,2% eram anti-HBc total / anti-HBs reagente e 42% anti-HBs isolado, atribuídos à vacinação; 41,7% receberam esquema vacinal completo e 58,3% eram suscetíveis. Conclusões: Os resultados encontrados podem ser utilizados como norteadores de ações estratégicas visando ampliar a cobertura vacinal e reduzir a prevalência de infectados na população de comunicantes intradomiciliares. (AU)

Objective: To evaluate the coverage of the hepatitis B vaccine and the frequency of infection in communicants of Hepatitis B virus carriers twenty years after the vaccine was implemented in the city of Belém, Pará, Brazil. Method: Quantitative descriptive study developed between 2016 and 2018. Home visits were carried out to the carriers of the virus notified through the search for communicants, with guiding on research, filling and signing forms, collecting samples for serological tests for Hepatitis B (HBsAg, total anti - HBc, anti - HBs) by immunoenzymatic technique. Results: In the population analyzed 53.5% are male, with a mean age of 9.4 years (ranging from 4 months to 19 years and median of 10 years). Carriers HBsAg reagent were not detected; total anti - HBc isolated was detected in 2.1%; 4.2% were total anti - HBc / anti - HBs reagent and 42% anti - HBs alone, attributed to vaccination; 41.7% received a complete vaccination schedule and 58.3% were susceptible. Conclusions:The results found can be used as guidelines for strategic actions aimed at expanding vaccine coverage and reducing the prevalence of infected people in the population of household communicators. (AU)

Objetivo: Evaluarla cobertura de la vacuna contra lahepatitis B y lafrecuencia de infecciónen portadores delVirus de laHepatitis Bveinteañosdespués de laimplementación de lavacuna enlaciudad de Belém, Pará, Brasil. Método: Estudiodescriptivocuantitativo realizado entre 2016 y 2018. Fueron realizadas visitas domiciliarias a los portadores del vírus, notificados a través de labúsqueda de domiciliares, conorientaciones sobre lainvestigación, registro y asignatura de formularios, toma de muestras de sangre para pruebas serológicas de Hepatitis B (HBsAg, anti-HBc total, anti-HBs) por la técnica inmunoenzimática. Resultados: Enlapoblaciónanalizada 53,5% del sexo masculino, conedadpromedio de 9,4 años (entre 4 meses a 19 añoscon mediana de 10 años) no fueron detectados portadores de HBsAgreactivo; el total de anti-HBcfué detectado en 2,1%; 4,2% anti-HBc total/anti-HBs reactivo, y, 42% anti-HBs aislado, atribuido a lavacunación; 41,7% recibieronel esquema completo de vacunación y 58,3% fueronsusceptibles. Conclusiones: Los resultados encontrados puedenusarse como pautas para acciones estratégicas dirigidas a ampliar la cobertura de vacunación y reducirlaprevalencia de personas infectadas enlapoblación de comunicadores domésticos. (AU)

Serological and molecular retrospective analysis of hepatitis E suspected cases from the Eastern Brazilian Amazon 1993-2014.

INTRODUCTION: We evaluated the anti-hepatitis E virus (HEV) antibody prevalence and HEV-RNA in archived serum samples of non-A-C hepatitis, or suspected cases of HEV infection from the Eastern Brazilian Amazon from 1993 to 2014. METHODS: Serum samples (n = 318) were tested using ELISA and immunoblotting, and screened for HEV-RNA by RT-qPCR. RESULTS: Anti-HEV IgM and IgG were detected in 3.4% (11/318) and 5.9% (19/318) of the samples, respectively. All samples were HEV-RNA negative. CONCLUSIONS: HEV was detected at a low prevalence. Broader serological and molecular evaluation of HEV infection in the Amazon region should be carried out.

A paruterinid metacestode in the liver of a Neotropical bat (Molossus molossus).

We describe a case of microscopic liver lesion caused by larval cestode in a frugivorous bat (Molossus molossus) from the Western Brazilian Amazon. Histopathological analysis of liver indicated the occurrence of metacestode associated with multifocal histiocytic response and the phylogenetic analysis of Cox-I and 18S rDNA genes indicated that the parasite belonged to the family Paruterinidae. This is the first identification of cestodes of the family Paruterinidae in bats and may suggest a broad range of paruterinid tapeworm hosts to be investigated in the Brazilian Amazon.

Serological and molecular retrospective analysis of hepatitis E suspected cases from the Eastern Brazilian Amazon 1993-2014

Abstract INTRODUCTION We evaluated the anti-hepatitis E virus (HEV) antibody prevalence and HEV-RNA in archived serum samples of non-A-C hepatitis, or suspected cases of HEV infection from the Eastern Brazilian Amazon from 1993 to 2014. METHODS Serum samples (n = 318) were tested using ELISA and immunoblotting, and screened for HEV-RNA by RT-qPCR. RESULTS Anti-HEV IgM and IgG were detected in 3.4% (11/318) and 5.9% (19/318) of the samples, respectively. All samples were HEV-RNA negative. CONCLUSIONS HEV was detected at a low prevalence. Broader serological and molecular evaluation of HEV infection in the Amazon region should be carried out.

Hepatitis E virus infection among rural Afro-descendant communities from the eastern Brazilian Amazon.

INTRODUCTION: The prevalence, public health impact, and epidemiological characteristics of hepatitis E virus (HEV) are poorly understood in Brazil. METHODS: Serum samples from 535 individuals from three rural Afro-descendant communities located in eastern Brazilian Amazon were collected in October 2015 and tested for presence of anti-HEV IgM and IgG antibodies. Serologically positive samples were also tested for HEV-RNA. RESULTS: Two cases were confirmed for anti-HEV IgM (0.3 %) and two cases for anti-HEV IgG (0.3 %). No sample was positive for HEV-RNA. CONCLUSIONS: Results indicated low prevalence of HEV infection in Afro-descendant rural communities from the eastern Brazilian Amazon.

Hepatitis E virus infection among rural Afro-descendant communities from the eastern Brazilian Amazon

Abstract INTRODUCTION The prevalence, public health impact, and epidemiological characteristics of hepatitis E virus (HEV) are poorly understood in Brazil. METHODS Serum samples from 535 individuals from three rural Afro-descendant communities located in eastern Brazilian Amazon were collected in October 2015 and tested for presence of anti-HEV IgM and IgG antibodies. Serologically positive samples were also tested for HEV-RNA. RESULTS Two cases were confirmed for anti-HEV IgM (0.3 %) and two cases for anti-HEV IgG (0.3 %). No sample was positive for HEV-RNA. CONCLUSIONS Results indicated low prevalence of HEV infection in Afro-descendant rural communities from the eastern Brazilian Amazon.

A novel hepatitis B virus species discovered in capuchin monkeys sheds new light on the evolution of primate hepadnaviruses.

BACKGROUND & AIMS: All known hepatitis B virus (HBV) genotypes occur in humans and hominoid Old World non-human primates (NHPs). The divergent woolly monkey HBV (WMHBV) forms another orthohepadnavirus species. The evolutionary origins of HBV are unclear. METHODS: We analysed sera from 124 Brazilian monkeys collected during 2012-2016 for hepadnaviruses using molecular and serological tools, and conducted evolutionary analyses. RESULTS: We identified a novel orthohepadnavirus species in capuchin monkeys (capuchin monkey hepatitis B virus [CMHBV]). We found CMHBV-specific antibodies in five animals and high CMHBV concentrations in one animal. Non-inflammatory, probably chronic infection was consistent with an intact preCore domain, low genetic variability, core deletions in deep sequencing, and no elevated liver enzymes. Cross-reactivity of antisera against surface antigens suggested antigenic relatedness of HBV, CMHBV, and WMHBV. Infection-determining CMHBV surface peptides bound to the human HBV receptor (human sodium taurocholate co-transporting polypeptide), but preferentially interacted with the capuchin monkey receptor homologue. CMHBV and WMHBV pseudotypes infected human hepatoma cells via the human sodium taurocholate co-transporting polypeptide, and were poorly neutralised by HBV vaccine-derived antibodies, suggesting that cross-species infections may be possible. Ancestral state reconstructions and sequence distance comparisons associated HBV with humans, whereas primate hepadnaviruses as a whole were projected to NHP ancestors. Co-phylogenetic analyses yielded evidence for co-speciation of hepadnaviruses and New World NHP. Bayesian hypothesis testing yielded strong support for an association of the HBV stem lineage with hominoid ancestors. Neither CMHBV nor WMHBV was likely the ancestor of the divergent human HBV genotypes F/H found in American natives. CONCLUSIONS: Our data suggest ancestral co-speciation of hepadnaviruses and NHP, and an Old World origin of the divergent HBV genotypes F/H. The identification of a novel primate hepadnavirus offers new perspectives for urgently needed animal models of chronic hepatitis B. LAY SUMMARY: The origins of HBV are unclear. The new orthohepadnavirus species from Brazilian capuchin monkeys resembled HBV in elicited infection patterns and could infect human liver cells using the same receptor as HBV. Evolutionary analyses suggested that primate HBV-related viruses might have emerged in African ancestors of New World monkeys millions of years ago. HBV was associated with hominoid primates, including humans and apes, suggesting evolutionary origins of HBV before the formation of modern humans. HBV genotypes found in American natives were divergent from those found in American monkeys, and likely introduced along prehistoric human migration. Our results elucidate the evolutionary origins and dispersal of primate HBV, identify a new orthohepadnavirus reservoir, and enable new perspectives for animal models of hepatitis B.

Detection of Toxoplasma gondii antibodies in captive non-human primates in the Amazon region, Brazil.

BACKGROUND: Toxoplasma gondii infections in captive non-human primates are of interest because often they die due to severe toxoplasmosis. Thus, we aimed to evaluate samples from a serum bank to T. gondii antibodies. METHODS: Serum samples of 179 monkeys from the National Center of Primates, Brazil, were retrospective analyzed for T. gondii IgG antibodies by modified agglutination test using formalin-fixed whole parasites as antigen (cutoff 1:25). RESULTS: Among the 179 samples tested, 88 (49.2%) were positive. Twelve of the 18 evaluated species presented at least one positive animal. A higher occurrence of positive animals was found in New World (52.2%) than Old World (22.2%) monkeys (P = .023) and in the animals from domestic donation origin, which had lived in human homes as pets (P = .004). CONCLUSIONS: We confirm the widespread presence of T. gondii in captive monkeys and contribute to the range of species that can be infected by this parasite.

SEROLOGICAL DETECTION OF HEPATITIS A VIRUS IN FREE-RANGING NEOTROPICAL PRIMATES (Sapajus spp., Alouatta caraya) FROM THE PARANÁ RIVER BASIN, BRAZIL.

Nonhuman primates are considered as the natural hosts of Hepatitis A virus (HAV), as well as other pathogens, and can serve as natural sentinels to investigate epizootics and endemic diseases that are of public health importance. During this study, blood samples were collected from 112 Neotropical primates (NTPs) (Sapajus nigritus and S. cay, n = 75; Alouatta caraya, n = 37) trap-captured at the Paraná River basin, Brazil, located between the States of Paraná and Mato Grosso do Sul. Anti-HAV IgG antibodies were detected in 4.5% (5/112) of NTPs, specifically in 6.7% (5/75) of Sapajus spp. and 0% (0/37) of A. caraya. In addition, all samples were negative for the presence of IgM anti-HAV antibodies. These results suggest that free-ranging NTPs were exposed to HAV within the geographical regions evaluated.

SEROLOGICAL DETECTION OF HEPATITIS A VIRUS IN FREE-RANGING NEOTROPICAL PRIMATES (Sapajus spp., Alouatta caraya) FROM THE PARANÁ RIVER BASIN, BRAZIL

Nonhuman primates are considered as the natural hosts of Hepatitis A virus (HAV), as well as other pathogens, and can serve as natural sentinels to investigate epizootics and endemic diseases that are of public health importance. During this study, blood samples were collected from 112 Neotropical primates (NTPs) (Sapajus nigritus and S. cay, n = 75; Alouatta caraya, n = 37) trap-captured at the Paraná River basin, Brazil, located between the States of Paraná and Mato Grosso do Sul. Anti-HAV IgG antibodies were detected in 4.5% (5/112) of NTPs, specifically in 6.7% (5/75) of Sapajus spp. and 0% (0/37) of A. caraya. In addition, all samples were negative for the presence of IgM anti-HAV antibodies. These results suggest that free-ranging NTPs were exposed to HAV within the geographical regions evaluated.

First report of equine Pegivirus in South America, Brazil.

The human Pegivirus (HPgV, also known as GBV-C virus or hepatitis G virus) is a lymphotropic RNA-virus phylogenetically related to the Hepatitis C virus, which infects approximately 5% of the world's human population. Recently, two novel, presumably hepatotropic, pegiviruses, designated as equine Pegivirus (EPgV) and Theiler's Disease Associated Virus (TDAV), were discovered in horses with clinical and laboratory evidence of hepatic disease. To verify the occurrence of pegiviruses infection in horses from Pará State, northern Brazil, serum samples from 114 horses located in four cities (Acará, Belém, Dom Eliseu and Ananindeua) were submitted for the molecular analysis of EPgV by nested RT-PCR. The results of nucleotide sequencing and phylogenetic analysis of EPgV NS3 and NS5B genomic regions confirmed one positive sample among 114 tested samples (1/114; 0.8%). No evidence of TDAV infection was found, but despite the low prevalence and unknown clinical significance among the studied population, these results represent the first molecular detection of EPgV in horses in South America.

Avaliação do hemograma em pacientes tratados para hepatite C / Evaluation of blood cell count in patients treated for chronic hepatitis C at Fundação Santa Casa de Misericórdia do Pará

Objetivo: avaliar as alterações do hemograma em pacientes tratados para hepatite C crônica com interferon peguilado (PEG-IFN) e ribavirina (RBV) no Ambulatório do Fígado da Fundação Santa Casa de Misericórdia do Pará. Método: estudo transversal, realizado através de análise de 52 prontuários com aplicação de protocolos de pesquisa, posteriormente, submetidos à avaliação estatística. Resultados: observou-se queda nos níveis de hemoglobina, em ambos os sexos, mais importante nos três primeiros meses de tratamento. A anemia foi mais intensa com 6 meses após início da terapia. Ocorreu queda progressiva dos valores de leucócitos durante o primeiro ano de acompanhamento, caracterizando leucopenia a partir do sexto mês, com melhora após término do tratamento. Não houve ocorrência de plaquetopenia durante o período de acompanhamento. Conclusão: constatou-se a ocorrência de discrasia sanguínea durante o tratamento com PEG-IFN associado à RBV, caracterizada por anemia e leucopenia. No entanto, não houve trombocitopenia no período de acompanhamento.

Objective: to evaluate changes in blood cell count of pacients treated for chronic hepatis C with pegylated interferon (PEG - IFN) and ribavirin (RBV) at "Ambulatório do Fígado da Fundação Santa Casa de Misericórdia do Pará". Method: transversal study with 52 patient's records by implementation of research protocols subsequently analyzed statistically. Results: there was a reduction in hemoglobin levels in both sexes, more important during the first three months of treatment. Anemia was more severe with 6 months of therapy. There was a reduction in leukocytes during the first year of follow-up, featuring leukopenia at the sixth month with improvement after the end of treatment. There was no occurrence of thrombocytopenia during the monitoring period. Conclusion: occurrence of blood dyscrasias during treatment with PEG - IFN in combination with RBV, characterized by anemia and leukopenia. However, there was no thrombocytopenia during the follow-up.

Aspectos epidemiológicos de pacientes com doença renal crônica e hepatite C submetidos a hemodiálise em Belém (PA) / Epidemiological aspects of patients with chronic kidney disease and hepatitis C infection on hemodialysis in Belém (PA)

Objetivo: Avaliar o perfil epidemiológico de pacientes com doença renal crônica e hepatite C submetidos a hemodiálise em Belém (PA). Método: estudo transversal realizado através de protocolos auto-aplicáveis em 46 pacientes matricu-lados em 5 unidades de Hemodiálise de Belém (PA), nos meses de agosto e setembro de 2010. Resultados: a maioria dos pacientes era do sexo masculino, sendo a nefropatia diabética a principal doença de base (43,5%). A incidência de Hepatite C após início de tratamento dialítico foi de 67,4%, a idade média de infecção foi menor nos pacientes que tiveram diagnóstico durante a hemodiálise, o tempo de hemodiálise maior que 5 anos e realizar diálise em diferentes serviços demonstraram maior risco de infecção, além disso, houve alteração dos níveis de alanina aminotrasferase (ALT) de 11 pacientes antes, durante e após a soroconversão. Conclusão: pacientes submetidos a hemodiálise tem risco maior de infecção pelo Vírus da Hepatite C (VHC) do que na população em geral, sendo necessária permanente vigilância e controle nos fatores de risco associados.

Revista Paraense de Medicina - V.28 (1) janeiro-março 2014 19Objective: The purpose of this study was to evaluate epidemiological aspects of patients with chronic kidney disease and hepatitis C infection on hemodialysis in Belem (PA). Methods: transversal, retrospective and prospective study was conducted through analysis of self-applicable protocols of 46 patients during August and September of 2010. Re-sults: the prevalence of male witch diabetic nephropathy was the first cause of chronic kidney disease (43,5%), 67,4% were anti-HCV positive after starting dialysis treatment, the average age was lower in patients diagnosed during hemodialysis,time of dialysis longer than 5 years and hemodialysis in different services have an increased risk for HCV infection, ALT average of 11 patients were significant a month before seroconversion, in month with anti-HCV positive and a month after seroconversion. Final Considerations: Patients in hemodialysis have important risk factors for Hepatitis C infection requiring permanent surveillance.

Association of killer cell immunoglobulin-like receptor polymorphisms with chronic hepatitis C and responses to therapy in Brazil.

Soroprevalence for Hepatitis C virus is reported as 2.12% in Northern Brazil, with about 50% of the patients exhibiting a sustained virological response (SVR). Aiming to associate polymorphisms in Killer Cell Immunoglobulin-like Receptors (KIR) with chronic hepatitis C and therapy responses we investigated 125 chronic patients and 345 controls. Additionally, 48 ancestry markers were genotyped to control for population stratification. The frequency of the KIR2DL2 and KIR2DL2+HLA-C(Asp80) gene and ligand was higher in chronic infected patients than in controls (p < 0.0009, OR = 3.4; p = 0.001, OR = 3.45). In fact, KIR2DL3 is a weaker inhibitor of NK activity than KIR2DL2, which could explain the association of KIR2DL2 with chronic infection. Moreover, KIR2DS2 and KIR2DS2+HLA-C(Asp80) (p < 0.0001, OR = 2.51; p = 0.0084, OR = 2.62) and KIR2DS3 (p < 0.0001; OR = 2.57) were associated with chronic infection, independently from KIR2DL2. No differences in ancestry composition were observed between control and patients, even with respect to therapy response groups. The allelic profile KIR2DL2/KIR2DS2/KIR2DS3 was associated with the chronic hepatitis C (p < 0.0001; OR = 3). Furthermore, the patients also showed a higher mean number of activating genes and a lower frequency of the homozygous AA profile, which is likely secondary to the association with non-AA and/or activating genes. In addition, the KIR2DS5 allele was associated with SVR (p = 0.0261; OR = 0.184).The ancestry analysis of samples ruled out any effects of population substructuring and did not evidence interethnic differences in therapy response, as suggested in previous studies.

Anatomo-clinical and molecular description of liver neotropical echinococcosis caused by Echinococcus oligarthrus in human host.

Since humans rarely play the role as Echinococcus oligarthrus host, there is lack of knowledge about the complex infectious process. Only three cases have been reported to occur in humans in the neotropics until now. We present the anatomo-clinical and molecular findings describing a new case of infection by E. oligarthrus in a man. The muscular or subcutaneous tissues tropism described for this species in the previously reported cases was not present, but a liver tropism was observed. Additionally, the larval stage rostellar hooks morphometry differed from E. oligarthrus in the other human cases.

HEV infection in swine from Eastern Brazilian Amazon: evidence of co-infection by different subtypes.

Hepatitis E virus (HEV) is a fecal-orally transmitted member of the genus Hepevirus that causes acute hepatitis in humans and is widely distributed throughout the world. Pigs have been reported as the main source of genotypes 3 and 4 infection to humans in non-endemic areas. To investigate HEV infection in pigs from different regions of Pará state (Eastern Brazilian Amazon), we performed serological and molecular analyses of serum, fecal and liver samples from 151 adult pigs slaughtered between April and October 2010 in slaughterhouses in the metropolitan region of Belém, Pará. Among the animals tested, 8.6% (13/151) were positive for anti-HEV IgG but not for anti-HEV IgM. HEV RNA was detected in 4.8% (22/453) of the samples analyzed and 9.9% (15/151) of the animals had at least one positive sample. Phylogenetic analysis showed that all sequences belonged to genotype 3 that were related to human isolates from other non-endemic regions, suggesting that the isolates had zoonotic potential. Subtypes 3c and 3f were simultaneously detected in some pigs, suggesting co-infection by more than one strain and/or the presence of a recombinant virus. These results constitute the first molecular and serologic evidence of swine HEV circulation in the Eastern Brazilian Amazon.

Prevalência de marcadores sorológicos do vírus da hepatite B em profissionais de saúde de um laboratório de pesquisa na Amazônia oriental, Estado do Pará, Brasil, 2007 a 2009 / Prevalence of serological markers of hepatitis B virus in health professionals from a research laboratory in the eastern Amazon, State of Pará, Brazil, 2007 to 2009

OBJETIVO: determinar a prevalência dos marcadores sorológicos da infecção pelo vírus da hepatite B (VHB) entre trabalhadores de um instituto de pesquisas na Amazônia oriental, estado do Pará, Brasil. MÉTODOS: estudo descritivo, desenvolvido entre 2007 e 2009, com trabalhadores que concordaram em participar mediante entrevista e investigação dos marcadores sorológicos da hepatite B, por técnicas imunoenzimáticas. RESULTADOS: entre 528 trabalhadores pesquisados, encontrou-se prevalência de 0,4 por cento do antígeno de superfície do VHB, 8,0 por cento anticorpos contra o antígeno core do VHB/anticorpos contra o antígeno de superfície do VHB, 2,5 por cento anticorpos contra o antígeno core do VHB isolado e 28,8 por cento anticorpos contra o antígeno de superfície do VHB isolado, entre 68,4 por cento de suscetíveis ao VHB que correspondiam aos indivíduos não vacinados. CONCLUSÃO: identificou-se prevalência e soroconversão inadequadas, abaixo da média informada pelo Ministério da Saúde, em que três doses da vacina devem conferir proteção de aproximadamente 90,0 por cento em adultos.

OBJECTIVE: to determine the prevalence of serological markers of infection by hepatitis B virus (HBV) among workers at a research institute in eastern Amazon, state of Pará, Brazil. METHODS: descriptive study, carried between 2007 and 2009, with workers who agreed to participate through interview and investigation of serological markers of hepatitis B by immu-noenzymatic techniques. RESULTS: among 528 individuals surveyed, was found the prevalence of 0,4 per cent of surface antigen of HBV, 8.0 per cent of antibodies against hepatitis B core antigen/antibody against the surface antigen of VHB, 2.5 per cent antibodies against hepatitis B core isolated antigen and 28.8 per cent antibodies against surface antigen of isolated HBV, 68.4 per cent susceptible to HBV that corresponded to non-vaccinated individuals. CONCLUSION: the research identified inadequate prevalence of seroconversion below the average reported by the Ministry of Health, in which three doses of the vaccine should confer protection of approximately 90.0 per cent in adults.

Identification of a long-standing colony of Proechimys at the Instituto Evandro Chagas, Pará, Brazil, based on cytogenetic information / Identificação de uma colonia de longo prazo de Proechimys no Instituto Evandro Chagas, Pará, Brasil, com base em informações citogenéticas

The taxonomic classification of the genus Proechimys is complex because many of its species are morphologically similar but chromosomally different, with diploid (2n) values ranging from 14 to 62. The "Seção de Criação e Produção de Animais de Laboratório do Instituto Evandro Chagas" (The Division for Breeding and Production of Laboratory Animals, Instituto Evandro Chagas, Brazil) maintains a Proechimys colony for biomedical research. The colony members have been classified as P. guyannensis, which reportedly has 2n=40 and a fundamental number (FN) = 54. However, using karyotype analysis to aid in their taxonomic classification, we instead observed that a sample of the animals in this colony have 2n = 30 and FN = 56, with a medium-sized submetacentric X chromosome and a small acrocentric Y chromosome. Constitutive heterochromatin was distributed as follows: in the pericentromeric regions of chromosomes 6, 7, 9, 10, 11, 12, 13, 14 and X; on the distal short arms of chromosomes 3, 6, 10 and X; on the distal long arm of chromosome 12; on the long arm of the Y chromosome; and distally on both arms of chromosomes 7, 9 and 11. The nucleolar organizer regions (NORs) are located on the long arm of chromosome 9. This karyotype is consistent with that described previously for P. roberti, but not P. guyannensis, thus demonstrating the importance of using karyotyping for the taxonomic identification of Proechimys.

A classificação taxonómica do gênero Proechimys é complexa porque muitas de suas espécies são morfologicamente semelhantes, porém diferentes cromossomicamente, com números de diploide (2n) que variam entre 14 e 62. A Seção de Criação e Produção de Animais de Laboratório do Instituto Evandro Chagas mantém uma colónia de Proechimys para pesquisa biomédica. Os membros da colónia foram classificados como P. guyannensis, que possui 2n = 40 e um número fundamental (NF) = 54. No entanto, ao utilizar a análise do cariótipo para auxiliar em sua classificação taxonómica, observamos que uma amostra dos animais desta colónia possuem 2n = 30 e NF = 56, com um cromossomo X submetacêntrico de tamanho médio e um cromossomo Y acrocêntrico pequeno. A heterocromatina constitutiva foi distribuída da seguinte forma: nas regiões pericentromérica dos cromossomos 6, 7, 9, 10, 11, 12, 13, 14 e X; na porção distal dos braços curtos dos cromossomos 3, 6, 10 e X; na porção distal do braço longo do cromossomo 12; no braço longo do cromossomo Y; e nas porções distais de ambos os braços dos cromossomos 7, 9 e 11. As regiões organizadoras nucleolares (NORs) localizam-se no braço longo do cromossomo 9. Este cariótipo é consistente com o descrito anteriormente para P. roberti, não para P. guyannensis, o que demonstra a importância do uso de cariotipagem para a identificação taxonómica de Proechimys.