Ranavirus

Ranavirus is a group of viruses that belong to a family called Iridoviridae. This family has several types of viruses, but Ranavirus is special because it can make amphibians and reptiles sick. Amphibians include animals like frogs and salamanders.

Besides affecting amphibians and reptiles, Ranavirus is also one of three types in this virus family that can infect teleost fishes. The other two types that can infect fish are called Lymphocystivirus and Megalocytivirus. These viruses are important to study because they can cause diseases in many aquatic animals.

Ecological impact

Ranaviruses are viruses that can make many kinds of fish very sick, both in the wild and on farms. This can cause big losses in fish numbers, which matters for the fishing industry.

Ranaviruses can also harm amphibian populations around the world. Their impact on amphibians is similar to that of a harmful fungus that makes these animals sick. Scientists have found Ranavirus outbreaks in many places, but they are seen more often in some areas, showing that more watching is needed in those spots.

Etymology

The word "Rana" comes from the Latin word for "frog". Scientists gave this name because they first found a Ranavirus in the 1960s inside a Northern leopard frog (Lithobates pipiens).

Evolution

Ranaviruses likely started in a virus that affected fish. Later, this virus began to infect amphibians and reptiles too.

Hosts

Ranavirus can make many animals sick, especially frogs and some turtles and lizards. Frogs that can get sick include wood frogs, American bullfrogs, and pickerel frogs. Some endangered frogs can also be affected.

Some reptiles that can get this virus include green pythons, Burmese star tortoises, leopard tortoises, and many kinds of lizards and turtles like the mountain lizard and red-eared sliders.

Taxonomy

The genus Ranavirus includes several different viruses, named after the animals they affect. Examples are Common midwife toad virus-E and Frog virus 3.

The family Iridoviridae has seven groups of viruses, and Ranavirus is one of them. Ranavirus can infect frogs, salamanders, and some fish. It is related to two other groups called Lymphocystivirus and Megalocytivirus.

Structure

Ranaviruses are big viruses that look like balls. They are about 150 nanometers across. They contain DNA, which is a type of genetic material. DNA has instructions for making about 100 different parts of the virus. The outside of these viruses is mostly made of a special protein called the major capsid protein.

Replication

Ranaviruses, like Frog virus 3, can grow inside host cells between 12 and 32 degrees Celsius. They enter cells by attaching to special parts and moving in. Inside, the virus takes off its coat and goes to the cell’s control center, called the nucleus. There, it starts making copies of its genetic material. The virus then moves this material to another part of the cell to keep copying it, forming long strands of DNA. These strands are packed into new virus particles that can infect other cells. The virus’s genetic material is circular and has extra pieces of DNA at the ends.

DNA repair

A type of ranavirus from Chinese giant salamanders makes a protein that helps fix DNA damage in cells by putting broken pieces back together.

Transmission

Ranaviruses can spread in different ways. They can spread through dirty soil, touching animals that are sick, or being in water that has the virus. Animals can also spread the virus when they eat other infected animals. The virus can stay in water for a long time, even when there are no animals around.

Epizoology

Ranaviruses have made many frogs and other amphibians very sick and die in places like Asia, Europe, North America, and South America. Scientists have found these viruses in wild amphibians in Australia, but they have not caused large groups of animals to die there.

Pathogenesis

When a virus gets inside a cell, it begins to make its proteins very fast. This can make the cell stop working right or even break apart in just a few hours.

Seasonal disease dynamics

Scientists have noticed that some diseases caused by Ranavirus happen more often in certain seasons. These viruses grow best between 8-30 °C, and they grow faster when it’s warmer. This leads to more disease cases in the warm summer months.

Young frogs, especially when they are getting ready to change into adults, have weaker immune systems. This makes them more vulnerable to the virus. Because of this, many cases of disease in frogs in the United States happen between June and August.

Environmental persistence

We don't know much about how long ranaviruses can survive in nature. In normal outdoor conditions, a certain type of ranavirus can last about one day. How long the virus stays around probably depends on things like temperature and tiny living things in the water.

Scientists have looked for places where the virus might hide, which could help explain how it stays in amphibian groups. Some frogs or salamanders that don't get very sick from the virus might carry it and spread it to younger animals. Because ranaviruses can infect many different animals, fish and reptiles might also help the virus survive. Studies have shown that the virus can move between different kinds of animals.

Gross pathology

When animals get sick from Ranavirus, they might look red and swollen. They could have bleeding under their skin, swollen limbs, and livers that seem puffy and delicate.