age: 101
school: lalalala
location: allalalala
likes: lalalalala
dislikes: lala
...i love lalalala...
a fairy's diary
[Tuesday, April 04, 2006]
the spell was cast: 7:11 PM
RESULTS AND DISCUSSION
Of the 15 samples of Rattus norvegicus, 8 were infested with Polyplax sp. and mesostigmatids, each having a 26.7% rate of infestation. On the other hand, 12 of 15 individuals of Mus musculus were infested mainly with Polyplax sp. accounting for an 80.0% rate of infestation. No mesostigmatids like those found in R. norvegicus were isolated from M. musculus (Table 1).
Table 1. Identification and % infestation rate of the ectoparasites isolated from the rodent species.
Ectoparasite
Rattus norvegicus
n= 15
Mus musculus
n=15
No. of infested samples
% infestation rate
No. of infested samples
% infestation rate
Polyplax sp.
4
26.7%
12
80.0%
Mesostigmatids (gamasids)
4
26.7%
0
0
Total
8/15
53.3%
12/15
80.0%
Eight of fifteen R. norvegicus samples examined were infected with Hymenolepis sp. and Rictularia sp. accounting for 46.7% and 6.7% rate of infection, respectively. On the contrary, 5 of 15 M. musculus samples were infected mainly with Hymenolepis sp. with 33.3% rate of infection. No Rictularia sp. was isolated from M. musculus (Table 2).
Table 2. Identification and % infection rate of the endoparasites isolated from the rodent species.
Endoparasite
Rattus norvegicus
n= 15
Mus musculus
n=15
No. of infested samples
% infestation rate
No. of infested samples
% infestation rate
Hymenolepis sp.
7
46.7%
5
33.3%
Rictularia sp.
1
6.7%
0
0
Total
8/15
53.3%
5/15
33.3%
M. musculus has a higher infestation rate of 80.0% compared to R. norvegicus which is 53.3%. Polyplax sp. Was the only ectoparasite isolated from M. musculus. In contrast, R. norvegicus are highly infected with endoparasites having 53.3% rate of infection compared to M. musculus with an infection rate of 33.3%. Hymenolepis sp. accounts for the high infection rate for both rodent species. The over-all percent prevalence of parasites for both rodent species is 76.7%. 11 of 15 R. norvegicus were positive for ectoparasites and/or endoparasites. Comparatively, 12 of 15 M. musculus, are infested and/or infected.
Polyplax sp., a sucking louse isolated from both rodents, was observed to have blunt heads, which are narrow than the body. Their bodies are slender with scales. The have segmented antennaes and 3 pairs of legs (Fig. 1).
The mesostigmatids isolated from Rattus norvegicus was observed to have round bodies, bearing 4 pairs of legs without pincers. A pair of pointed structures could also be seen projecting from the anterior part (Fig 2). The mesostigmatids could not be identified up to the genus level because other distinguishing structures are not clear as seen in the prepared slides. The specimens are resistant to clearing with potassium hydroxide solution due to the preservative solution used.
Tapeworms from the genus Hymenolepis sp. isolated from both rodents were identified based on the number and arrangement of the testes—3 lobes forming a straight line — and also on the appearance of the scolex and rostellum Fig 3). Two species were identified: Hymenolepis nana, with unarmed suckers and armed but small rostellum, and Hymenolepis diminuta, with small suckers and small, unarmed rostellum.
The nematode isolated from Rattus norvegicus was observed to be mature females of the genus Rictularia sp. The worms have two longitudinal rows of backward projecting hook-like spines that extend from the anterior down to some distance posteriorly. The buccal capsule is well-sclerotized while the esophagus’ opening is surrounded by three serrated lancets (Fig 4).
Ewing (1929) documented that Polyplax spinulosa, also called the common sucking louse of rats, occurs on all of the domestic rats and is almost worldwide in distribution. Another species, Polyplax serrata, has been documented as a common parasite of the house mouse in Europe. This species of Polyplax has also been found on the house mouse in the United States only on laboratory animals. Polyplax species belong to the family Haematopinidae and members of this sucking lice family are confined largely to rodents, insectivores and ungulates. In a study conducted by Eduardo and Mercado (1982), Polyplax spinulosa accounted for 27% infection rate and ranked third among the seven ectoparasites they isolated from R. norvegicus. This study and the previous studies suggest that Polyplax sp. may be among the common ectoparasites of rodents.
One species from the Order Mesostigmata that commonly infest rats is the tropical rat mite, Ornithonyssus bacoti, family Dermanyssidae. O. bacoti is found worldwide, in both temperate and tropical climates. This species can retard growth and eventually kill young mice. These mites do not transmit any pathogens to humans but it was found experimentally that they can transmit plague, ricketssialpox, Q fever and murine typhus (Schmidt 1992).
The results obtained in this study for parasite infection on rodents agree with previous literatures describing parasite species such as Polyplax and Hymenolepis as common parasites of rodents. Tapeworms such as Hymenolepis sp., for example, have already been established in rodent host species (McArthur, 1999). Studies by Morozov (1960) showed Rictularia species such as R. cristata isolated from rodents in Eastern Europe. Another species, R. proni was also found in the intestine of the rodent Apodemus sylvaticus by Quentin (1970), and Quentin et al. (1973) in France (Anderson, 2000).
The greater variety of parasite species isolated from R. norvegicus can be attributed to their preferred habitats such as garbage dumps, sewers, open fields, and basements (Armitage, 2004). In these settings, they are more prone in making contact with various ectoparasites such as fleas and mites, and also to intermediate hosts of endoparasites such as fleas, cockroaches and the like (McArthur, 1999).
