Marcia Helena Braga Catroxo

By M.H.B. Catroxo, A.M.C.R.P.F. Martins, S. Petrella and L. Milanelo

Part of the book: A Bird's-Eye View of Veterinary Medicine

By M.H.B. Catroxo and A.M.C.R.P.F. Martins

Transmission electron microscopy has been an excellent tool, essential for the diagnosis of bacterial and viral animal diseases. Four basic techniques have been widely used: negative staining (rapid preparation), immunoelectron microscopy, immunolabeling with colloidal gold particles and resin embedding. The negative staining technique (rapid preparation) is the most applied, due to its speed, simplicity and specificity and can be used in various clinical specimens – such as feces, semen, urine, serum, organ fragments, crusts, body fluids, cell culture suspension, oral, ocular and fecal swabs, among others –, in which the agents can be directly viewed in large numbers in the samples. The immunoelectron microscopy technique using a specific primary antibody promotes the clumping of particles, also allowing the serotyping of the agents. In the immunolabeling with colloidal gold technique antigen-antibody reaction is enhanced by marking the antigen colloidal gold particles associated with protein A. The method of resin embedding, followed by ultrathin sections of cells or infected tissues can monitor the different stages of maturation viruses or bacteria and their behavior inside of host cells by determining not only the infection, but also the course of the disease in farms. The techniques can be applied to all animal species, either large or small, including aquatic and wild animals. Its implementation allows rapid diagnosis, providing subsidies for the immediate institution of prophylactic measures, and control and prevention of bacterial and viral animal diseases.

Part of the book: The Transmission Electron Microscope

By Marcia Helena Braga Catroxo and Ana Maria Cristina Rebello Pinto da Fonseca Martins

Gastroenteritis caused by viruses is considered to be one of the most important diseases in livestock, being the main cause of morbidity and mortality in young animals, culminating in serious economic losses due to costs with prophylaxis and treatment, increased susceptibility of animals to secondary infections, developmental delay and death. Stressful factors may support the onset of illness. Several viral agents can cause gastroenteritis in various animal species. Rotaviruses are considered the main cause of enteric infections in various animals, including humans constituting important zoonosis. Due to genetic diversity and their ability to cross the species barrier, the coronaviruses infect many species. In cattle, they cause “Winter Dysentery” in adult animals and “Neonatal Diarrhea” in newborn calves. In swine, they are responsible for “Transmissible Gastroenteritis” and “Swine Epidemic Diarrhea.” Equines infected with coronavirus also develop severe gastroenteritis. Bovine viral diarrhea (BVD) caused by a flavivirus of the genus Pestivirus is related to digestive and reproductive disorders, affecting any productive sector, are it cut, milk or confinement. Transmission electron microscopy is an indispensable tool in the diagnosis of viral gastroenteric infectious diseases. Negative staining is a simple, fast and efficient technique, being ideal for the detection of gastroenteric viruses, being easily visualized. The immunoelectron microscopy (IEM) technique allows increasing the sensitivity of virus detection where low concentrations of virus are aggregated so that they may be more easily seen. The immunolabeling with colloidal gold technique utilizes specific antibodies tagged with particles of colloidal gold to label the antigen antibody reaction. Embedding resin technique allows obtaining information on the virus–cell interaction. The different transmission electron microscopy modalities promotes a fast and accurate diagnosis of the different gastroenteric viral agents, allowing prophylactic measures of control and prevention in the creations to be promptly instituted, avoiding animal losses and disastrous economic losses, and collaborating with the National Porcine and Bovine Agribusiness.

Part of the book: Stomach Disorders