THE INFLUENCE OF INFECTION WITH NOSEMA APIS ON THE ACTIVITIES AND LONGEVITY OF THE WORKER HONEYBEE

Abstract

Infection of the adult worker honeybee with Nosema apis reduces or obviates brood feeding and causes her to commence foraging earlier than a healthy bee. The length of foraging activity and the total length of life of infected bees is reduced.In colonies infected with N . apis the rate of brood rearing is severely depressed during April, May and June, the degree of depression being proportional to the percentage infection.Infection decreases during July, August and September, and consequently the rate of brood rearing increases, but the resulting addition in foraging population is usually too late to increase the honey crop.A worker honeybee normally performs brood-rearing duties in the hive for approximately 18 days and then joins the foraging population. Rosch (1925, 1927, 1930)~ Nelson (1927) and Haydak (1932) have shown, however, that a bee can adapt her activity to the requirements of the colony. Ribbands (1950) demonstrated that household bees can be caused to forage at an unusually early age, and that bees that have been foraging for pollen can be made to collect nectar instead by anesthetization with carbon dioxide. Hassanein (1951) noted that infection of the worker honeybee by Nosema apisretards or inhibits development of the pharyngeal salivary glands, making it difficult or impossible for infected bees to feed the young larvae. Farrar (1947), in his work on the influence of Nosema disease on brood production by recently installed package bees, measured the amount of sealed brood present in each of the new colonies 3 weeks after they had been placed on clean, drawn combs, and attempted to correlate these measurements with the percentage of adult bees infected with N . apis. He obtained correlation coefficients of -0.31 in 1945 and -0.42 in 1946. He recorded that newly installed packages of bees having 60-100% of the workers infected with N . apis produced in the 3 weeks after installation an average of 100-125 sq.in. less sealed brood than comparable packages of healthy bees.The experiments described below were made to explore more fully the effects of Nosema infection on brood-rearing and on the foraging and longevity of individual bees.

Outcome of Colonization of Apis mellifera by Nosema ceranae

“…Infection of workers by N. apis retards or inhibits development of the pharyngeal salivary (33), compromising the feeding of young larvae. A fairly high proportion of the eggs laid by the queen of a colony suffering from nosemosis fail to produce pupae, while artificially infected pupae are resistant to infection (14). The bee population begins to decrease as Nosema infection spreads.…”

“…Direct evidence of the influence of the parasite on colonies is related to changes in the activity and longevity of the worker honeybee and queen (10,14). Infection of workers by N. apis retards or inhibits development of the pharyngeal salivary (33), compromising the feeding of young larvae.…”

The Role of Colony Organization on Pathogen Transmission in Social Insects

“…Once a worker grows old and switches to tasks outside the nest, a resident pathogen that infects only the brood or younger workers will have fewer opportunities to find other susceptible hosts and its transmission within the colony will be slower. This is why the precocious foraging observed in honeybees infected by the protozoan, Nosema apis (Hassanein, 1953;L'Arrivee, 1963;Wang & Moeller, 1970) or the sacbrood virus (Bailey & Fernando, 1972) could be a host adaptation to reduce the rate of disease transmission within the colony. Such a role for the speed of age polyethism schedule in pathogen transmission has also been proposed by SchmidHempel & Schmid-Hempel (1993) to explain their demonstration that rapidly multiplying variants of the trypanosome Crithidia bombi show a higher within-colony transmission than slower ones in the bumblebee, Bombus terrestris.…”

Shorter-lived workers start foraging earlier

“…There is an especially large body of data about honeybee pathogens (Morse and Flottum, 1997). Honeybee workers infected with Nosema apis start foraging earlier (Hassanein, 1953;Wang and Moeller, 1970;Woyciechowski and Moroń, 2009) and are more likely to collect food even during unfavorable weather (Woyciechowski and Kozłowski, 1998). In one study the precocious foraging of workers inoculated with Nosema spores was not confirmed, but there was no certainty that the inoculation was effective (Mattila and Otis, 2006).…”