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Meal Beetle Larvae as Intermediate Hosts of the Poultry Tapeworm Raillietina cesticillus
Meal Beetle Larvae as Intermediate Hosts of the Poultry Tapeworm Raillietina cesticillus GEORGE W.
LUTTERMOSER
U. S. Bureau of Animal Industry (Received for publication August 29, 1939)
ORSFALL (1938) demonstrated experimentally that the adults of the common meal beetles, Tribolium castaneum and T. confusum, serve as suitable intermediate hosts for the following poultry tapeworms: Hymenolepis carioca, Choanotaenia injundibulum, and Raillietina cesticillus. The question naturally arose regarding the susceptibility of the larvae of these meal beetles to infection with the cysticercoids of various species of poultry tapeworms. Experiments were undertaken, therefore, to test this point. Three species of tapeworms, namely, Raillietina cesticillus, R. echinobothrida, and Hymenolepis carioca were used in the experiments recorded in this paper. Larvae, pupae, and adults of meal beetles, exposed to infection as larvae, were fed to chickens to determine whether the insects harbored infective cysticercoids. The results obtained* in these investigations are reported in the following pages. MATERIAL AND METHODS
The beetle larvae used in the experiments reported in this paper were obtained by holding adult meal beetles for several weeks in battery jars containing bran. Under these conditions the beetles mated and produced eggs from which larvae hatched. The adult meal beetles were collected from the surface of feed sacks stored in the attic of a barn at the Agricultural Research Center, Beltsville, Maryland. This barn is located several hundred yards
from the nearest poultry yard; consequently, the beetles had no opportunity to become infected with parasites by swallowing the droppings from tapeworm-infected birds or in other ways. Gravid segments of H. carioca, R. echinobothrida, and R. cesticillus were collected from the droppings of infected birds, placed on pieces of moistened paper toweling, and offered to several hundred beetle larvae which were confined in Petri dishes. As a control, gravid segments were offered to a similar number of adult meal beetles in the same manner as those offered to the larvae. Gravid tapeworm segments were offered to the adult and larval beetles at least five times over a period of 7 to 10 days. After the third day, a small amount of bran was added to each of the dishes and on the tenth day all the dishes were filled with bran; several small pieces of potato were added as food for the insects. Four to six weeks following the initial feeding of the tapeworm segments, some of the larval and adult beetles were dissected and examined for cysticercoids. At this time, some of the beetle larvae were found to have transformed to pupae and adults. Several specimens of each of these stages of the beetles were examined for cysticercoids. All cysticercoids recovered were fed to young parasite-free chickens in order to determine the infectivity of the tapeworms for their definitive host. In order to ascertain whether beetle larvae would eat the gravid tapeworm seg-
[177]
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178
GEORGE W. LUTTERMOSER TABLE 1.—Results of experimental infection of meal beetles and chickens with poultry tapeworms Beetles1 Chickens Exposed to infection
Tapeworm
Hymenolepsis carioca
Raillietina cesticillus
1 2 3
Stage
Number
Stage of beetle
Cysticercoids found (number)
Larva
1072
Larva Pupa Adult
28 14 30
0 0 0
Adult
1052
Adult
50
10.0
Larva
702
Larva Pupa Adult
13 17 10
0 0 0
0 0 0
Adult
76
s
Adult
50
0
0
Larva
1013
Larva Pupa Adult
47 28 26
70.2 28.6 28.5
Adult
2063
Adult
206
80.3
Av. cystiPercentage cercoids per beetle infected (number) 0 0 0 0.2
Number fed beetles
Percentage infected
None 1 1
0 0
3
33.3
None None 1
0
1
0
6.7 3.0 2.3
17 2 4
64.0 50.0 50.0
11.5
15
86.6
Mostly Tribolium confusum; a few T. castaneum. Some of these beetles were not examined but were fed to chickens. All these beetles were examined and some of the cysticercoids developing in them were fed to chickens.
ments in the presence of an abundance of other food, gravid segments of R. cesticillus were offered to a large number of meal beetle larvae confined in a Petri dish filled with bran. The results of this experiment are discussed elsewhere in this paper. EXPERIMENTAL DATA The results of the experimental feeding of the gravid segments of three species of poultry tapeworms to larvae and adults of the meal beetles, T. castaneum and T. confusum, and the subsequent feeding of the cysticercoids to chicks, are given in Table 1. In those experiments involving the feeding of segments of H. carioca, only the adult meal beetles became infected with the cysticercoids of this tapeworm. In a second series of experiments involving the feeding of segments of R. cesticillus, both larval and adult meal beetles contained cysticercoids, whereas neither larval nor adult beetles became infected with cysticercoids of R. echinobothrida as a re-
sult of feeding them gravid segments of this tapeworm. The results of the experiments indicate that the adults of the meal beetles are more suitable intermediate hosts for R. cesticillus than are the larval beetles, since 80.3 percent of the adults and only 70.2 percent of the larvae examined contained cysticercoids. Also, a larger average number of cysticercoids was found in the adults (11.5) than in the larvae (6.7). Cysticercoids of R. cesticillus were also found in the pupae and young adult beetles which developed from larvae to which gravid segments of this tapeworm had been offered. The incidence of infection found in the pupae and adult beetles (approximately 28 percent in each group) which developed from the larvae fed segments of R. cesticillus was less than one-half that found in the larval beetles (70.2), and the average number of cysticercoids in the pupae (3) and adults (2.3) was less than one-half that found in the larvae (6.7). Observations revealed no marked difference
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on May 30, 2015
Raillietina echinobothrida
Results of infection
MEAL BEETLE LARVAE AS INTERMEDIATE HOSTS OF POULTRY TAPEWORM
DISCUSSION
The larger number of cysticercoids found in the adults of Tribolium spp. than in the larvae of these insects following exposure to gravid segments of R. cesticUlus, may be due to the fact that the adults either ingested the tapeworm eggs more readily or that they are more suitable hosts. The higher average number of cysticercoids found in the larvae than in the pupae and adult beetles which as larvae were fed gravid tapeworm segments may be explained on the grounds that these larvae had been delayed in their metamorphosis due to the acquisition of initial heavy cysticercoid infections (the cultures were not examined until 4 to 6 weeks after the initial feeding of mature tapeworm segments). The smaller number of cysticercoids found in the pupae and adult beetles may have been due to the destruction of some of the cysticercoids during the process of metamorphosis of the infected larvae. This demonstration that the larvae and pupae of Tribolium spp. can serve experimentally as intermediate hosts for the poultry tapeworm, R. cesticUlus, suggests the possibility that other cestodes of poultry may be spread by larvae of meal beetles and also by the larvae of related beetles. ECONOMIC IMPORTANCE OF MEAL BEETLES Horsfall (1938) reported the adult meal
beetles, Tribolium castaneum and T. conjusum, as being suitable experimental intermediate hosts for H. carioca, C. infundibulum, and R. cesticUlus and the likelihood that these insects may spread tapeworm infection on poultry farms. The present study shows that the larvae and pupae of these cosmopolitan meal beetles are potential carriers of the widespread poultry tapeworm, R. cesticUlus. Since it has already been reported by Harwood and Luttermoser (1938) and Ackert and Case (1938), that heavy infections of R. cesticUlus retard the growth of young chickens, attention is again called to the importance of keeping feed free from meal beetles and away from chicken feces. SUMMARY
I. The larvae of the cosmopolitan meal beetles, Tribolium castaneum and T. conjusum, were experimentally infected with the common chicken tapeworm, Raillietina cesticUlus. Pupae and adult insects developing from infected beetle larvae were also found to be infected with cysticercoids of R. cesticUlus. Evidence is presented to show that the process of metamorphosis of the beetles from larvae to pupa, or pupa to adult does not destroy all of the cysticercoids present. II. The larvae became infected when offered the gravid segments of R. cesticUlus in the presence of either a large or a small amount of food, such as bran. REFERENCES
Ackert, J. E., and A. A. Case, 1938. Effects of the tapeworm, Raillietina cesticUlus (Molin) on growing chickens. J. Parasitol. 24 (supplement). P. 14. Harwood, Paul D., and George W. Luttermoser, 1938. The influence of infections with the tapeworm, Raillietina cesticUlus, on the growth of chickens. Proc. Helm. Soc. Wash. 5:60-62. Horsfall, Margery W., 1938. Meal beetles as intermediate hosts of poultry tapeworms. Poultry Sci. 17:8-11.
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on May 30, 2015
in the rate of development of the cysticercoids of R. cesticUlus in the different stages of the different species of meal beetles used in the experiments. The larvae of the meal beetles seemed to ingest tapeworm segment material readily even when there was an abundance of bran. The larvae reared under these conditions were found to be as heavily infected with cysticercoids of R. cesticUlus as those that were fed gravid tapeworm segments for the first 3 days in the absence of bran.
179
LUTTERMOSER
U. S. Bureau of Animal Industry (Received for publication August 29, 1939)
ORSFALL (1938) demonstrated experimentally that the adults of the common meal beetles, Tribolium castaneum and T. confusum, serve as suitable intermediate hosts for the following poultry tapeworms: Hymenolepis carioca, Choanotaenia injundibulum, and Raillietina cesticillus. The question naturally arose regarding the susceptibility of the larvae of these meal beetles to infection with the cysticercoids of various species of poultry tapeworms. Experiments were undertaken, therefore, to test this point. Three species of tapeworms, namely, Raillietina cesticillus, R. echinobothrida, and Hymenolepis carioca were used in the experiments recorded in this paper. Larvae, pupae, and adults of meal beetles, exposed to infection as larvae, were fed to chickens to determine whether the insects harbored infective cysticercoids. The results obtained* in these investigations are reported in the following pages. MATERIAL AND METHODS
The beetle larvae used in the experiments reported in this paper were obtained by holding adult meal beetles for several weeks in battery jars containing bran. Under these conditions the beetles mated and produced eggs from which larvae hatched. The adult meal beetles were collected from the surface of feed sacks stored in the attic of a barn at the Agricultural Research Center, Beltsville, Maryland. This barn is located several hundred yards
from the nearest poultry yard; consequently, the beetles had no opportunity to become infected with parasites by swallowing the droppings from tapeworm-infected birds or in other ways. Gravid segments of H. carioca, R. echinobothrida, and R. cesticillus were collected from the droppings of infected birds, placed on pieces of moistened paper toweling, and offered to several hundred beetle larvae which were confined in Petri dishes. As a control, gravid segments were offered to a similar number of adult meal beetles in the same manner as those offered to the larvae. Gravid tapeworm segments were offered to the adult and larval beetles at least five times over a period of 7 to 10 days. After the third day, a small amount of bran was added to each of the dishes and on the tenth day all the dishes were filled with bran; several small pieces of potato were added as food for the insects. Four to six weeks following the initial feeding of the tapeworm segments, some of the larval and adult beetles were dissected and examined for cysticercoids. At this time, some of the beetle larvae were found to have transformed to pupae and adults. Several specimens of each of these stages of the beetles were examined for cysticercoids. All cysticercoids recovered were fed to young parasite-free chickens in order to determine the infectivity of the tapeworms for their definitive host. In order to ascertain whether beetle larvae would eat the gravid tapeworm seg-
[177]
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on May 30, 2015
H
178
GEORGE W. LUTTERMOSER TABLE 1.—Results of experimental infection of meal beetles and chickens with poultry tapeworms Beetles1 Chickens Exposed to infection
Tapeworm
Hymenolepsis carioca
Raillietina cesticillus
1 2 3
Stage
Number
Stage of beetle
Cysticercoids found (number)
Larva
1072
Larva Pupa Adult
28 14 30
0 0 0
Adult
1052
Adult
50
10.0
Larva
702
Larva Pupa Adult
13 17 10
0 0 0
0 0 0
Adult
76
s
Adult
50
0
0
Larva
1013
Larva Pupa Adult
47 28 26
70.2 28.6 28.5
Adult
2063
Adult
206
80.3
Av. cystiPercentage cercoids per beetle infected (number) 0 0 0 0.2
Number fed beetles
Percentage infected
None 1 1
0 0
3
33.3
None None 1
0
1
0
6.7 3.0 2.3
17 2 4
64.0 50.0 50.0
11.5
15
86.6
Mostly Tribolium confusum; a few T. castaneum. Some of these beetles were not examined but were fed to chickens. All these beetles were examined and some of the cysticercoids developing in them were fed to chickens.
ments in the presence of an abundance of other food, gravid segments of R. cesticillus were offered to a large number of meal beetle larvae confined in a Petri dish filled with bran. The results of this experiment are discussed elsewhere in this paper. EXPERIMENTAL DATA The results of the experimental feeding of the gravid segments of three species of poultry tapeworms to larvae and adults of the meal beetles, T. castaneum and T. confusum, and the subsequent feeding of the cysticercoids to chicks, are given in Table 1. In those experiments involving the feeding of segments of H. carioca, only the adult meal beetles became infected with the cysticercoids of this tapeworm. In a second series of experiments involving the feeding of segments of R. cesticillus, both larval and adult meal beetles contained cysticercoids, whereas neither larval nor adult beetles became infected with cysticercoids of R. echinobothrida as a re-
sult of feeding them gravid segments of this tapeworm. The results of the experiments indicate that the adults of the meal beetles are more suitable intermediate hosts for R. cesticillus than are the larval beetles, since 80.3 percent of the adults and only 70.2 percent of the larvae examined contained cysticercoids. Also, a larger average number of cysticercoids was found in the adults (11.5) than in the larvae (6.7). Cysticercoids of R. cesticillus were also found in the pupae and young adult beetles which developed from larvae to which gravid segments of this tapeworm had been offered. The incidence of infection found in the pupae and adult beetles (approximately 28 percent in each group) which developed from the larvae fed segments of R. cesticillus was less than one-half that found in the larval beetles (70.2), and the average number of cysticercoids in the pupae (3) and adults (2.3) was less than one-half that found in the larvae (6.7). Observations revealed no marked difference
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on May 30, 2015
Raillietina echinobothrida
Results of infection
MEAL BEETLE LARVAE AS INTERMEDIATE HOSTS OF POULTRY TAPEWORM
DISCUSSION
The larger number of cysticercoids found in the adults of Tribolium spp. than in the larvae of these insects following exposure to gravid segments of R. cesticUlus, may be due to the fact that the adults either ingested the tapeworm eggs more readily or that they are more suitable hosts. The higher average number of cysticercoids found in the larvae than in the pupae and adult beetles which as larvae were fed gravid tapeworm segments may be explained on the grounds that these larvae had been delayed in their metamorphosis due to the acquisition of initial heavy cysticercoid infections (the cultures were not examined until 4 to 6 weeks after the initial feeding of mature tapeworm segments). The smaller number of cysticercoids found in the pupae and adult beetles may have been due to the destruction of some of the cysticercoids during the process of metamorphosis of the infected larvae. This demonstration that the larvae and pupae of Tribolium spp. can serve experimentally as intermediate hosts for the poultry tapeworm, R. cesticUlus, suggests the possibility that other cestodes of poultry may be spread by larvae of meal beetles and also by the larvae of related beetles. ECONOMIC IMPORTANCE OF MEAL BEETLES Horsfall (1938) reported the adult meal
beetles, Tribolium castaneum and T. conjusum, as being suitable experimental intermediate hosts for H. carioca, C. infundibulum, and R. cesticUlus and the likelihood that these insects may spread tapeworm infection on poultry farms. The present study shows that the larvae and pupae of these cosmopolitan meal beetles are potential carriers of the widespread poultry tapeworm, R. cesticUlus. Since it has already been reported by Harwood and Luttermoser (1938) and Ackert and Case (1938), that heavy infections of R. cesticUlus retard the growth of young chickens, attention is again called to the importance of keeping feed free from meal beetles and away from chicken feces. SUMMARY
I. The larvae of the cosmopolitan meal beetles, Tribolium castaneum and T. conjusum, were experimentally infected with the common chicken tapeworm, Raillietina cesticUlus. Pupae and adult insects developing from infected beetle larvae were also found to be infected with cysticercoids of R. cesticUlus. Evidence is presented to show that the process of metamorphosis of the beetles from larvae to pupa, or pupa to adult does not destroy all of the cysticercoids present. II. The larvae became infected when offered the gravid segments of R. cesticUlus in the presence of either a large or a small amount of food, such as bran. REFERENCES
Ackert, J. E., and A. A. Case, 1938. Effects of the tapeworm, Raillietina cesticUlus (Molin) on growing chickens. J. Parasitol. 24 (supplement). P. 14. Harwood, Paul D., and George W. Luttermoser, 1938. The influence of infections with the tapeworm, Raillietina cesticUlus, on the growth of chickens. Proc. Helm. Soc. Wash. 5:60-62. Horsfall, Margery W., 1938. Meal beetles as intermediate hosts of poultry tapeworms. Poultry Sci. 17:8-11.
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on May 30, 2015
in the rate of development of the cysticercoids of R. cesticUlus in the different stages of the different species of meal beetles used in the experiments. The larvae of the meal beetles seemed to ingest tapeworm segment material readily even when there was an abundance of bran. The larvae reared under these conditions were found to be as heavily infected with cysticercoids of R. cesticUlus as those that were fed gravid tapeworm segments for the first 3 days in the absence of bran.
179