Amoeba

Malpighamoeba mellificae is the organism that causes amoeba disease. Since this protozoan is found in the Malpighian tubules of adult bees, diagnosis can be made only by the removal and microscopic examination of the tubules for the presence of amoeba cysts. The cysts measure 5-8 µm in diameter and can be seen in the infected Malpighian tubules.

The Malpighian tubules are long, threadlike projections originating at the junction of the midgut and the hindgut. The tubules can be teased away from the digestive tract with a pair of fine tweezers and then placed in a drop of water on a microscope slide. A cover glass is positioned over the tubules while applying uniform pressure to obtain a flat surface for microscopic examination. Malpighamoeba mellificae can be discerned using a high dry objective and then changing to the oil immersion objective for more detail.

Gregarines

Four gregarines (protozoans of the order Gregarinida) are associated with honey bees: Monoica apis, Apigregarina stammeri, Acuta rousseaui, and Leidyana apis. The immature stages, or cephalonts, average about 16 by 44 µm. Cephalonts are oval and consist of two distinct body segments; the posterior segment is larger. The mature stages, or sporonts, average about 35 by 85 µm and have a reduced anterior segment.

Gregarines are found attached to the epithelium of the midgut of adult honey bees. Gently remove the midgut from the digestive tract of a suspect bee and place it on a microscope slide in a drop of water. The midgut can be separated from the digestive tract at the point of attachment with the proventriculus (honey stomach) and hindgut using fine tweezers and a scalpel. Gently break open the midgut with fine tweezers and a probe, and place a cover glass over the resulting suspension. Gregarines can be seen using the low-power objective of a compound microscope.

Flagellates

Crithidia (= Leptomonas) species are the flagellates associated with honey bees. Flagellates have been found either free in the lumen or attached to the epithelium of the hiudgut and rectum of adult honey bees (Fyg 1954). Flagellates vary in size from 5 to 30 µm. Some appear as pearlike bodies with flagella; others are long threadlike forms or are round without flagella (Lotmar 1946). To look for flagellates, remove the digestive tract of a suspect bee and place it on a microscope slide in a drop of water. Then, using fine tweezers and a scalpel, separate the hindgut and rectum at the point of attachment with the midgut. Macerate the hindgut and rectum, using a fine pair of tweezers and a probe. Place a cover glass on the resulting suspension and observe under the high dry objective of the microscope.

Filamentous Virus

Filamentous virus is also known as F-virus and bee rickettsiosis. This disease, previously thought to be of rickettsial origin, can be diagnosed by examining the hemolymph of infected bees using phase-contrast microscopy. The hemolymph of honey bees infected with this virus is milky white and contains many spherical to rod-shaped viral particles of a size close to the limit of resolution for light microscopy. The viral particles consist of a folded nucleocapsid within a viral envelope and are 0.4 by 0.1 µm (Clark 1978b).