California
December 1997
In This Issue:
- Lesser Mealworm's Potential as a Reservoir for Salmonella and Other Enteric Bacteria
- Tapeworms and Their Control in Chickens
- Coming Events
Lesser Mealworm's Potential as a Reservoir for Salmonella and Other Enteric Bacteria Several beetles (order Coleoptera) can be found in the litter and manure of poultry. Some are considered pests because they can cause substantial structural damage to wood structures and Styrofoam insulation. Others on the other hand are considered to be beneficial since they feed on fly eggs and larvae. Beetles may also play a role in the transmission of avian disease. When poultry have access to their feces or litter, they will feed on the beetles they find. Several tape worms can be transmitted by beetles and a few bacterial and viral diseases may also be transmitted. In caged layer operations beetles have been considered most significant for their potential to cause structural damage to the poultry house or for their potential to suppress fly emergence.
Fig 1
Fig 2
Fig 3
Fig 4
Four common beetles found on poultry operations are the Lesser Mealworm or Darkling Beetle (Alphitobius diaperinus) (figure 1), Larder Beetle (Dermestes lardarius) (figure 2), Rove Beetle (Philonthus sp.) (figure 3), and the Hister Beetle (Carcinops pumilio) (figure 4). The Rove and Hister beetles are predators, which eat fly larvae and eggs, respectively. The Larder beetle feeds primarily on decomposing organic matter including feathers. The Lesser Mealworm beetle, however, can be an important pest both from the stand point of structural damage and disease transmission.
In 1994 McAllister, Steelman and Skeeles at the
Salmonella typhimurium was isolated for 16 days in 51 and 68% of the adult and larval lesser mealworm rinses respectively (external bodies). The bacteria was also isolated for 16 days from an average of 79 and 77% of the homogenized samples of larvae and adults, respectively. During this time, the beetles were exposed constantly to food that was inoculated a single time with S. typhimurium.
A significant number of larvae (78 percent) voided S. typhimurium in their feces for 17 days past the 24 hour feeding in experiment 2. Well over 50% of the adults were shedding the bacterium in their feces at 21 days post feeding, and 13% were still shedding bacteria at 28 days.
Table 1. Number of chicks with positive cloacal swabs for S. typhimurium 24 and 48 hours after eating infected lesser mealworms.
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No. of chicks/total tested
Number beetles and --------------------------------------
life stage fed to chicks 0 hr 24 hr 48 hr
----------------------------------------------------------------------Control larvae 0/5 0/5 0/5 Control adults 0/5 0/5 0/5 1 larva 0/10 9/10 9/10 1 adult 0/10 7/10 10/10 ----------------------------------------------------------------------
Table 1 gives the results of the chick feeding experiment. None of the chicks was positive for S. typhimurium prior to being fed the inoculated lesser mealworms. No chicks in the control group tested positive for Salmonella species either before or during the experiment. Nearly all of the chicks fed infected larva were positive by 24 hours and all of the chicks fed infected adult beetles were positive by 48 hours.
In
a second set of experiments McAllister, et al. (
E. coli was isolated from the exterior of all adults and larvae within 24 hours of infection. The number of positive samples decreased thereafter and by 14 days no bacteria were isolated from any of the beetles.
One hundred percent of beetle larvae and adults shed E. coli in their feces within the first 24 hours of being fed the inoculated chicken feed. Fifteen percent of the larvae continued to shed the organism at 6 days but none at 7 days. Fifteen percent of the adult beetles shed the bacteria for 10 days, but not beyond that.
Table 2. Number of chicks with positive cloacal swabs for E. coli after eating infected Lesser Mealworms.
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Life Stage and No. No. of positive chicks/total no. tested
of Beetles fed ---------------------------------------
to Chicks 0 hrs 24 hrs 48 hrs
--------------------------------------------------------------------Control larvae 0/5 0/5 0/5 Control adults 0/5 0/5 0/5 Larva (1) 0/5 1/5 2/5 Adult (1) 0/5 1/5 0/5 Larvae (5) 0/5 1/5 4/5
Adults (5) 0/5 1/5 2/5
--------------------------------------------------------------------
Like the earlier experiments with S. typhimurium all chicks were negative for the test organism at the beginning of the experiment and none of the control chicks became positive during the experiment. Feeding only one larva or adult resulted in a low rate of infection. Feeding up to five larvae or adults did not increase the infectivity at 24 hours, but did increase it by 48 hours post feeding.
Discussion
The lesser mealworm or Darkling beetle as it is sometimes called is capable of maintaining and shedding into the environment strains of bacteria that are pathogenic to poultry and humans. However, these experiments suggest that the beetle is less competent as a reservoir for E. coli than for S. typhimurium.
Because the lesser mealworm beetle can shed S. typhimurium in its feces for an extended period of time, it can potentially contaminate poultry feed and litter. This suggests that direct ingestion of the beetle by the bird my not be required to cause infection of poultry.
To our knowledge studies of this and other beetles acting as a reservoir for other Salmonella species have not been conducted; but these studies certainly point out the potential for arthropods contributing to the reservoir of other important pathogens such as S. enteritidis. The importance of good biosecurity and husbandry practices between flocks is emphasized by these results. Thorough removal of manure, feed and other debris, the use of registered insecticides, as well as increasing the time between flocks within the limits of replacement programs will help to reduce Lesser Mealworm beetle populations. Of course all other potential disease vectors such as rodents and birds should also be eliminated.
D.
R. Kuney
Area Poultry Farm Advisor
Tapeworms and Their Control in Chickens
Over the past couple of years we have been hearing about several cases of tape worm infestations in commercial laying flocks. The majority of these cases have been associated with cage-free flocks which is not surprising, however, a few cases have occurred in caged layers. At least one case was associated with poor laying performance.
Tape worms are so named because the adult stage resembles a measuring tape. Anatomically, the adult tapeworm is composed of a joined chain of segments called proglottids. At the anterior end of the adult is a hold-fast or attachment organ called a scolex for attachment to the tissue of the host. Immediately behind the scolex is a germinal center (neck) from which immature proglottids arise. Maturing proglottids proceed toward the posterior end of the worm. From the anterior to the posterior end of the chain there are groups of proglottids that progress from immature, to mature and then to gravid (full of eggs) segments. Each mature proglottid contains a complete set of male and female reproductive organs. The tapeworm does not have a digestive tract, so all nutrients must be absorbed through the body wall of the proglottids.
Most
tapeworms are relatively host specific. There are only about eight species
which appear in poultry in the
Table 1. Tapeworms known to infect chickens.
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Tapeworm Intermediate host Degree of pathogenicity
------------------------------------------------------------------------- Davainea proglottina Slug, snail Severe
Hymenolepis carioca Stable fly, beetle Unknown
Hymenolepis cantaniana Beetle Mild or harmless
Choanotaenia infundibulum Housefly, beetle Moderate
Amoebotaenia cuneata Earthworm Mild
Raillietina echinobothrida Ant Moderate to severe
Raillietina tetragona Ant Moderate to severe
Raillietina cesticillus Beetle Mild or harmless
-------------------------------------------------------------------------
The tapeworm life cycle can be quite complicated, sometimes involving 2 or more intermediate hosts. The basic life cycle begins with an adult tapeworm attached to the chicken gut wall (duodenum, jejunum or ileum). The worm sheds short chains of mature and gravid (containing eggs) proglottids into the lumen of the gut which is excreted with the feces. The intermediate host feeds on the excreted proglottids. The tapeworm eggs (onchospheres) become active and develop within the intermediate host to become an immature stage called a cysticercoid. The cysticercoid remains within the body cavity of the intermediate host until the host is eaten by the chicken. Digestive activity of the chicken releases the cysticercoid which then attaches to the gut of the bird. Most tapeworms require a 2-3 week period in the bird while the worm matures before the first gravid proglottids are released in the feces to begin a new cycle.
Prevention and control is primarily based on control and exclusion of the intermediate host. Identification of the species of tapeworm is valuable therefore in determining the identity of the intermediate host. Many times control of the intermediate host is a good management practice for reasons other than to control tapeworms. Housefly control will help eliminate infections of Choanotaenia infundibulum and will also minimize a public health nuiscance. Control of Lesser Mealworm beetles will eliminated infections of Raillietina cesticillus and will reduce structural damage to the poultry house.
D.R. Kuney
Coming
Events
*
Season's Greetings!
The
University of California
Douglas
R. Kuney, Monthly Editor
Area Poultry Farm Advisor
U.C. Cooperative Extension
21150 Box Springs Rd.
Moreno Valley, CA 92557
Tel. 909/683-6491 Ext. 226
FAX 909/788-2615
e-mail drkuney@citrus.ucr.edu
Ralph
A. Ernst,
Tel. 530/752-3513
FAX 530/752-8960
e-mail raernst@ucdavis.edu