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Brugia malayi in Mastomyscoucha: establishment in immunosuppressed animals
Acta Tropica 70 (1998) 157 – 162
Brugia malayi in Mastomys coucha: establishment in immunosuppressed animals K. Tyagi, P.K. Murthy, R.K. Chatterjee * Di6ision of Parasitology, Central Drug Research Institute, Lucknow 226001, India Received 25 September 1997; received in revised form 20 January 1998; accepted 28 January 1998
Abstract Investigations on various aspects of human filariasis using target filarial parasite, Brugia malayi is jeopardised to a great extent due to its prolonged incubation period and poor harvest from the existing experimental animal models. To obviate these difficulties it was contemplated to establish B. malayi infection in immunosuppressed Mastomys coucha. Cortisone, a well known immunosuppressant, was used at 10 mg/kg dose level subcutaneously in two courses each of 5 days duration. The first course was administered 1 week before and the second, a week after infective exposure. Mastomys were exposed either with 100 or 200 infective larvae (L3) each. Untreated age-matched animals were also exposed simultaneously. The minimum prepatent period was observed to be 90.7 days in immunosuppressed animals exposed to 200 L3. The course of microfilaraemia in immunosuppressed and control animals was identical upto 180 days of observation period. However, the adult worm recovery from the former group of Mastomys was higher. It is surmised that exposure with B. malayi L3 in immunosuppressed Mastomys would be of great advantage in getting larger harvests of adult worms of B. malayi. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Brugia malayi; Mastomys coucha; Cortisone; Immunosuppressed
* Corresponding author. Tel.: +91 522 212411 18, ext. 4315; fax: +91 522 223405/223938; e-mail: [email protected] 0001-706X/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII S0001-706X(98)00015-1
158
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
1. Introduction Brugia malayi, a subperiodic strain of human filarial infection has successfully been transmitted to various vertebrate hosts including monkeys, cats and rodents. (Edeson and Wharton, 1957; Schacher et al., 1969; Ash and Riley, 1970; Petranyi et al., 1975; Murthy et al., 1983, 1986, 1990; Tyagi et al., 1996). Among these Mastomys coucha is a small and hardy rodent commonly maintained as a laboratory animal. It is a good breeder and very suitable for cyclical maintenance of the infection. However, the main drawbacks are the prolonged incubation period and poor harvest of adult B. malayi which jeopardised the investigation on several aspects of human filariasis using target lymphatic dwelling filarial infection. To obviate these difficulties it was contemplated to establish B. malayi infection in immunosuppressed animals. The present study deals with the findings regarding the establishment of B. malayi in Mastomys pretreated with cortisone, a well known T-cell suppressant (Renoux and Renoux, 1980).
2. Materials and methods
2.1. Host: 8 -week-old male M. coucha 2.1.1. Parasite: subperiodic strain of B. malayi 2.1.1.1. Immunosuppressant. Cortisone (hydrocortisone acetate; Roussel) was used at 10 mg/kg, subcutaneously, for five consecutive days. Two courses of cortisone were given. First course was administered 1 week prior to infective exposure, i.e. on day −7 to −3 and second course was given on day + 7 to + 11 post exposure (Fig. 1). 2.2. Infecti6e exposure Infective larvae (L3) recovered from Aedes aegypti mosquitoes, fed 10 days before on microfilaraemic Mastomys, (Murthy et al., 1983) were injected, subcutaneously,
Fig. 1. Diagramatic representation of protocol for cortisone administration and infective exposure.
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
159
Table 1 Percent positivity for circulating mf and prepatent period in cortisone treated and untreated Mastomys Group of animals*
Number of L3 inoculated
Percent of positives
Prepatent period (Mean 9S.D.)*
C1 a E1 b C2 a E2 b
100 100 200 200
100 100 100 100
111.40 921.80 90.50 918.79 97.75 913.96 90.67 9 14.38
(5) (7) (6) (6)
(5) (7) (6) (6)
a
Cortisone untreated Mastomys. Cortisone treated Mastomys. * Number of animals in parenthesis.
b
on day ‘0’. Seven immunosuppressed and five normal animals constituting, respectively group E1 and C1 received 100 L3 each while six immunosuppressed and six normal animals, of group E2 and C2, received 200 L3 each (Table 1). The experiment was performed in two replicates using a total of 24 animals.
2.3. Assessment of establishment of infection 2.3.1. Duration of prepatent period Blood drawn (20 ml) at around 12:00 noon (Gupta et al., 1990) from each infected animal was examined initially on day 60 post exposure (p.e.) and thereafter at weekly intervals till microfilarae (mf) appeared in peripheral blood. 2.3.2. Parasitaemia Density of mf in peripheral blood (20 ml) was monitored by thick smear method till 180 days of infection. 2.3.3. Adult worm burden After 180 days of infection all infected animals were sacrificed under deep anaesthesia. Worm load was ascertained as described earlier (Murthy et al., 1983). Uterine content of female worms was examined according to the method of Lammler (1977). 2.4. Statistical analysis Significance was determined by student’s t-test.
3. Results Table 1 depicts the percent positivity for circulating mf and duration of prepatent period as observed in both immunosuppressed and control animals. It was seen that 100% animals of all the infected groups exhibited mf in their peripheral blood. The
160
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
duration of prepatent period among different groups of animals varied between 90.67 and 111.4 days (mean values) and minimum prepatent period (90.67 days) was observed in animals of group E2. The variations in prepatent period were not statistically significant. The course of mf was identical among all the groups till 180 days of observation period (data not shown). Fig. 2 depicts the percent recovery of adult B. malayi from both immunosuppressed as well as normal Mastomys. It is evident that immunosuppresed animals of group E1 and E2 exhibited, respectively, 18.75 9 8.04 and 22.929 0.49% (mean9 S.D.) adult worm establishment whereas the corresponding control Mastomys (belonging to group C1 and C2) showed, 10.89 4.87 and 11.089 4.9% adult worm recovery. The worm recovery from animals of group E2 only was found to be significantly high (PB 0.001).
4. Discussion B. malayi infection which can easily be transmitted to variety of vertebrate hosts (Edeson et al., 1955; Edeson and Wharton, 1957; Orihel and Pacheco, 1966; Ash and Riley, 1970; Murthy et al., 1983; Mak et al., 1990; Murthy et al., 1990), showed poor rate of establishment in these animals. However, large numbers of parasites could be recovered from gerbils/Jirds when exposed intraperitoneally (i.p.) (Ash and Riley, 1970; Mak et al., 1994) but the i.p. route of infection is not the natural mode of exposure hence results obtained with this host are less valuable for extrapolation to human infections. Moreover this rodent species is fragile, in that it can not be breed under extreme climatic conditions and also can not withstand repeated feeding of mosquitoes, which is necessary for cyclical maintenance of the infection. Therefore, the Mastomys is a more dependable host for carrying out studies on chemotherapeutic as well as various other aspects of human filariasis. In order to alter the prolonged prepatent period and low worm recovery, Mastomys
Fig. 2. Recovery of adult worms from immunosuppressed and normal Mastomys exposed to B. malayi L3.
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
161
were made immunosuppressed, prior to L3 exposure. The use of immunosuppressant in establishing various parasitic infections in refractory hosts (Bagai and Subrahmaniam, 1970; Cross et al., 1979) and the decisive role of T-cell activity in establishing helminthic infections (Nielson et al., 1974; Pollaco et al., 1978; Hammerberg et al., 1989) have been well documented. That is why, the immunosuppressant used in the present study was (cortisone) a T-cell suppressant. Initial experiments (data not shown) showed that the immunosuppression caused by single course of cortisone (10 mg/kg daily for 5 days) persisted for 15 days. Whereas, development of parasite from L3 to L5 takes about 35 days. Therefore, two courses of cortisone treatment were administered (as shown in Fig. 1) in such a fashion so that all the developing stages experienced the immunosuppressive state of the host. It was interesting to observe that the duration of the prepatent period in immunosuppressed mastomys as expected, was reduced though not to a statistically significant level. The adult worm recovery from immunosuppressed animals exposed to either 100 or 200 L3 was also improved (Fig. 2). However, the increase in the number of adult parasites from immunosuppressed Mastomys exposed to 100 L3 has no statistical significant whereas the large inoculum (200 L3/animal) exhibited significantly higher (P B0.001) worm recovery. Microfilarial density as observed in animals of all four groups was found to be similar up to 180 days. This observation period may be insufficient to study the course of microfilaraemia because in Mastomys it has been observed that peak mf counts appear at around 270 days post inoculation (Murthy et al., 1983). However, the aim of the present study was to observe the effect of immunosuppression on prepatent period and adult worm recovery, therefore, the animals were sacrificed at an early period. Nevertheless, it was also interesting to observe that most of the female worms recovered were gravid containing developing eggs and mf in their uteri. These findings thus indicate that the immunosuppressive effect of cortisone has resulted in obtaining a larger harvest of adult B. malayi with a shorter prepatent period.
Acknowledgements The award of Research Associateship by the Council of Scientific and Industrial Research, New Delhi to K.T. is gratefully acknowledged.
References Ash, L.R., Riley, J.M., 1970. Development of subperiodic Brugia malayi in the Jird. Meriones unguiculatus, with notes on infections in other rodents. J. Parasitol. 56, 969. Bagai, R.C., Subrahmaniam, D., 1970. Nature of acquired resistance to filarial infection in albino rats. Nature 228, 682. Cross, H.J., Partono, F., Hsu, M.K., Ash, L.R., Oemijati, S., 1979. Experimental transmission of Wuchereria bancrofti to monkey. Am. J. Trop. Med. Hyg. 28, 56. Edeson, J.F.B., Wharton, R.H., Buckely, J.J.C., 1955. Filarial parasites resembling Wuchereria malayi in domestic and forest animals in Malaya. Trans. R. Soc. Trop. Med. Hyg. 49, 604.
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K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
Edeson, J.F.B., Wharton, R.H., 1957. The transmission of Wuchereria malayi from man to the domestic cat. Trans. R. Soc. Trop. Med. Hyg. 51, 366. Gupta, C.K., Srivastava, M., Murthy, P.K., Tyagi, K., Mandal, S.K., Gunmala, Sen, A.B., 1990. Circadian periodicity in microfilarial counts. J. Trop. Med. Hyg. 93, 222 – 224. Hammerberg, B., Nogami, S., Nagasaki, K., Hayashi, Y., Tanaka, H., 1989. Protective immunity against Brugia malayi infective larvae in mice, II Induction by a T-cell dependant antigen isolated by monoclonal antibody affinity chromatography and SDS-PAGE. J. Immunol. 143, 4201 – 4207. Lammler, G., 1977. Experimental chemotherapy and chemoprophylaxis of filariasis. Pestic. Sci. 8, 563. Mak, J.W., Choong, M.F., Suresh, K., Lam, P.L.W., 1990. Experimental infection of the leaf-monkey, Presbytis cristata, with subperiodic Brugia malayi. Parasitol. Res. 76, 689 – 691. Mak, J.W., Sivanandam, S., Ngah, Z., Choong, M.F., 1994. Experimental infection of Meriones unguiculatus with subperiodic Brugia malayi Some parasitological observations. Malays. J. Sci. 15A, 9–11. Murthy, P.Q., Kalpana, Q., Tyagi, K., Roy Chowdhury, T.K., Sen, A.B., 1983. Susceptibility of Mastomys natalensis (GRA strain) to a subperiodic strain of human Brugia malayi. Ind. J. Med. Res. 77, 623–630. Murthy, P.K., Tyagi, K., Sen, A.B., 1986. Susceptibility of Macaca mulatta to a subperiodic strain of Brugia malayi. Ind. J. Parasitol. 10 (2), 189 – 192. Murthy, P.K., Tyagi, K., Chatterjee, R.K., 1990. Indian langur (Presbytis entellus) as experimental host of Brugia malayi infection. Curr. Sci. 59, 1236 – 1239. Nielson, K., Fogh, L., Anderson, S., 1974. Eosinophil response to migrating Ascaris suum larvae in normal and congenitally thymusless mice. Acta Pathol. Microbiol. Scand. 82, 919 – 920. Orihel, T.C., Pacheco, G., 1966. Brugia malayi in the Philippine macaque. J. Parasitol. 52, 394. Petranyi, G., Mieth, H., Leitner, I., 1975. Mastomys natalensis as an experimental host for Brugia malayi subperodic. SE Asian J. Trop. Med. Publ. Health 16, 328. Pollaco, S., Nicholas, W.L., Mitchell, G.F., Stewart, A.C., 1978. T-cell dependent collagenous encapsulating response in the mouse liver to Mesocestoides corti (cestoda). Int. J. Parasitol. 8, 457 – 462. Renoux, G., Renoux, M., 1980. The effects of sodium diethyldithiocarbamate, azathioprine, cyclophosphamide or hydrocortisone acetate administered along or in association for 4 weeks on the immune responses of Balb/c mice. Clin. Immunol. Immunopathol. 15, 23 – 32. Schacher, J.F., Sulahian, A., Edeson, J.F.B., 1969. Experimental lymphoedema in dogs infected with Brugia spp. Trans. R. Soc. Trop. Med. Hyg. 63, 682 – 684. Tyagi, K., Murthy, P.K., Chatterjee, R.K., 1996. Brugia malayi in Indian Leaf monkey (Presbytis entellus)—Response to repeated exposures of infective larvae. Curr. Sci. 70 (2), 164 – 167.
.
Brugia malayi in Mastomys coucha: establishment in immunosuppressed animals K. Tyagi, P.K. Murthy, R.K. Chatterjee * Di6ision of Parasitology, Central Drug Research Institute, Lucknow 226001, India Received 25 September 1997; received in revised form 20 January 1998; accepted 28 January 1998
Abstract Investigations on various aspects of human filariasis using target filarial parasite, Brugia malayi is jeopardised to a great extent due to its prolonged incubation period and poor harvest from the existing experimental animal models. To obviate these difficulties it was contemplated to establish B. malayi infection in immunosuppressed Mastomys coucha. Cortisone, a well known immunosuppressant, was used at 10 mg/kg dose level subcutaneously in two courses each of 5 days duration. The first course was administered 1 week before and the second, a week after infective exposure. Mastomys were exposed either with 100 or 200 infective larvae (L3) each. Untreated age-matched animals were also exposed simultaneously. The minimum prepatent period was observed to be 90.7 days in immunosuppressed animals exposed to 200 L3. The course of microfilaraemia in immunosuppressed and control animals was identical upto 180 days of observation period. However, the adult worm recovery from the former group of Mastomys was higher. It is surmised that exposure with B. malayi L3 in immunosuppressed Mastomys would be of great advantage in getting larger harvests of adult worms of B. malayi. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Brugia malayi; Mastomys coucha; Cortisone; Immunosuppressed
* Corresponding author. Tel.: +91 522 212411 18, ext. 4315; fax: +91 522 223405/223938; e-mail: [email protected] 0001-706X/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII S0001-706X(98)00015-1
158
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
1. Introduction Brugia malayi, a subperiodic strain of human filarial infection has successfully been transmitted to various vertebrate hosts including monkeys, cats and rodents. (Edeson and Wharton, 1957; Schacher et al., 1969; Ash and Riley, 1970; Petranyi et al., 1975; Murthy et al., 1983, 1986, 1990; Tyagi et al., 1996). Among these Mastomys coucha is a small and hardy rodent commonly maintained as a laboratory animal. It is a good breeder and very suitable for cyclical maintenance of the infection. However, the main drawbacks are the prolonged incubation period and poor harvest of adult B. malayi which jeopardised the investigation on several aspects of human filariasis using target lymphatic dwelling filarial infection. To obviate these difficulties it was contemplated to establish B. malayi infection in immunosuppressed animals. The present study deals with the findings regarding the establishment of B. malayi in Mastomys pretreated with cortisone, a well known T-cell suppressant (Renoux and Renoux, 1980).
2. Materials and methods
2.1. Host: 8 -week-old male M. coucha 2.1.1. Parasite: subperiodic strain of B. malayi 2.1.1.1. Immunosuppressant. Cortisone (hydrocortisone acetate; Roussel) was used at 10 mg/kg, subcutaneously, for five consecutive days. Two courses of cortisone were given. First course was administered 1 week prior to infective exposure, i.e. on day −7 to −3 and second course was given on day + 7 to + 11 post exposure (Fig. 1). 2.2. Infecti6e exposure Infective larvae (L3) recovered from Aedes aegypti mosquitoes, fed 10 days before on microfilaraemic Mastomys, (Murthy et al., 1983) were injected, subcutaneously,
Fig. 1. Diagramatic representation of protocol for cortisone administration and infective exposure.
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
159
Table 1 Percent positivity for circulating mf and prepatent period in cortisone treated and untreated Mastomys Group of animals*
Number of L3 inoculated
Percent of positives
Prepatent period (Mean 9S.D.)*
C1 a E1 b C2 a E2 b
100 100 200 200
100 100 100 100
111.40 921.80 90.50 918.79 97.75 913.96 90.67 9 14.38
(5) (7) (6) (6)
(5) (7) (6) (6)
a
Cortisone untreated Mastomys. Cortisone treated Mastomys. * Number of animals in parenthesis.
b
on day ‘0’. Seven immunosuppressed and five normal animals constituting, respectively group E1 and C1 received 100 L3 each while six immunosuppressed and six normal animals, of group E2 and C2, received 200 L3 each (Table 1). The experiment was performed in two replicates using a total of 24 animals.
2.3. Assessment of establishment of infection 2.3.1. Duration of prepatent period Blood drawn (20 ml) at around 12:00 noon (Gupta et al., 1990) from each infected animal was examined initially on day 60 post exposure (p.e.) and thereafter at weekly intervals till microfilarae (mf) appeared in peripheral blood. 2.3.2. Parasitaemia Density of mf in peripheral blood (20 ml) was monitored by thick smear method till 180 days of infection. 2.3.3. Adult worm burden After 180 days of infection all infected animals were sacrificed under deep anaesthesia. Worm load was ascertained as described earlier (Murthy et al., 1983). Uterine content of female worms was examined according to the method of Lammler (1977). 2.4. Statistical analysis Significance was determined by student’s t-test.
3. Results Table 1 depicts the percent positivity for circulating mf and duration of prepatent period as observed in both immunosuppressed and control animals. It was seen that 100% animals of all the infected groups exhibited mf in their peripheral blood. The
160
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
duration of prepatent period among different groups of animals varied between 90.67 and 111.4 days (mean values) and minimum prepatent period (90.67 days) was observed in animals of group E2. The variations in prepatent period were not statistically significant. The course of mf was identical among all the groups till 180 days of observation period (data not shown). Fig. 2 depicts the percent recovery of adult B. malayi from both immunosuppressed as well as normal Mastomys. It is evident that immunosuppresed animals of group E1 and E2 exhibited, respectively, 18.75 9 8.04 and 22.929 0.49% (mean9 S.D.) adult worm establishment whereas the corresponding control Mastomys (belonging to group C1 and C2) showed, 10.89 4.87 and 11.089 4.9% adult worm recovery. The worm recovery from animals of group E2 only was found to be significantly high (PB 0.001).
4. Discussion B. malayi infection which can easily be transmitted to variety of vertebrate hosts (Edeson et al., 1955; Edeson and Wharton, 1957; Orihel and Pacheco, 1966; Ash and Riley, 1970; Murthy et al., 1983; Mak et al., 1990; Murthy et al., 1990), showed poor rate of establishment in these animals. However, large numbers of parasites could be recovered from gerbils/Jirds when exposed intraperitoneally (i.p.) (Ash and Riley, 1970; Mak et al., 1994) but the i.p. route of infection is not the natural mode of exposure hence results obtained with this host are less valuable for extrapolation to human infections. Moreover this rodent species is fragile, in that it can not be breed under extreme climatic conditions and also can not withstand repeated feeding of mosquitoes, which is necessary for cyclical maintenance of the infection. Therefore, the Mastomys is a more dependable host for carrying out studies on chemotherapeutic as well as various other aspects of human filariasis. In order to alter the prolonged prepatent period and low worm recovery, Mastomys
Fig. 2. Recovery of adult worms from immunosuppressed and normal Mastomys exposed to B. malayi L3.
K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
161
were made immunosuppressed, prior to L3 exposure. The use of immunosuppressant in establishing various parasitic infections in refractory hosts (Bagai and Subrahmaniam, 1970; Cross et al., 1979) and the decisive role of T-cell activity in establishing helminthic infections (Nielson et al., 1974; Pollaco et al., 1978; Hammerberg et al., 1989) have been well documented. That is why, the immunosuppressant used in the present study was (cortisone) a T-cell suppressant. Initial experiments (data not shown) showed that the immunosuppression caused by single course of cortisone (10 mg/kg daily for 5 days) persisted for 15 days. Whereas, development of parasite from L3 to L5 takes about 35 days. Therefore, two courses of cortisone treatment were administered (as shown in Fig. 1) in such a fashion so that all the developing stages experienced the immunosuppressive state of the host. It was interesting to observe that the duration of the prepatent period in immunosuppressed mastomys as expected, was reduced though not to a statistically significant level. The adult worm recovery from immunosuppressed animals exposed to either 100 or 200 L3 was also improved (Fig. 2). However, the increase in the number of adult parasites from immunosuppressed Mastomys exposed to 100 L3 has no statistical significant whereas the large inoculum (200 L3/animal) exhibited significantly higher (P B0.001) worm recovery. Microfilarial density as observed in animals of all four groups was found to be similar up to 180 days. This observation period may be insufficient to study the course of microfilaraemia because in Mastomys it has been observed that peak mf counts appear at around 270 days post inoculation (Murthy et al., 1983). However, the aim of the present study was to observe the effect of immunosuppression on prepatent period and adult worm recovery, therefore, the animals were sacrificed at an early period. Nevertheless, it was also interesting to observe that most of the female worms recovered were gravid containing developing eggs and mf in their uteri. These findings thus indicate that the immunosuppressive effect of cortisone has resulted in obtaining a larger harvest of adult B. malayi with a shorter prepatent period.
Acknowledgements The award of Research Associateship by the Council of Scientific and Industrial Research, New Delhi to K.T. is gratefully acknowledged.
References Ash, L.R., Riley, J.M., 1970. Development of subperiodic Brugia malayi in the Jird. Meriones unguiculatus, with notes on infections in other rodents. J. Parasitol. 56, 969. Bagai, R.C., Subrahmaniam, D., 1970. Nature of acquired resistance to filarial infection in albino rats. Nature 228, 682. Cross, H.J., Partono, F., Hsu, M.K., Ash, L.R., Oemijati, S., 1979. Experimental transmission of Wuchereria bancrofti to monkey. Am. J. Trop. Med. Hyg. 28, 56. Edeson, J.F.B., Wharton, R.H., Buckely, J.J.C., 1955. Filarial parasites resembling Wuchereria malayi in domestic and forest animals in Malaya. Trans. R. Soc. Trop. Med. Hyg. 49, 604.
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K. Tyagi et al. / Acta Tropica 70 (1998) 157–162
Edeson, J.F.B., Wharton, R.H., 1957. The transmission of Wuchereria malayi from man to the domestic cat. Trans. R. Soc. Trop. Med. Hyg. 51, 366. Gupta, C.K., Srivastava, M., Murthy, P.K., Tyagi, K., Mandal, S.K., Gunmala, Sen, A.B., 1990. Circadian periodicity in microfilarial counts. J. Trop. Med. Hyg. 93, 222 – 224. Hammerberg, B., Nogami, S., Nagasaki, K., Hayashi, Y., Tanaka, H., 1989. Protective immunity against Brugia malayi infective larvae in mice, II Induction by a T-cell dependant antigen isolated by monoclonal antibody affinity chromatography and SDS-PAGE. J. Immunol. 143, 4201 – 4207. Lammler, G., 1977. Experimental chemotherapy and chemoprophylaxis of filariasis. Pestic. Sci. 8, 563. Mak, J.W., Choong, M.F., Suresh, K., Lam, P.L.W., 1990. Experimental infection of the leaf-monkey, Presbytis cristata, with subperiodic Brugia malayi. Parasitol. Res. 76, 689 – 691. Mak, J.W., Sivanandam, S., Ngah, Z., Choong, M.F., 1994. Experimental infection of Meriones unguiculatus with subperiodic Brugia malayi Some parasitological observations. Malays. J. Sci. 15A, 9–11. Murthy, P.Q., Kalpana, Q., Tyagi, K., Roy Chowdhury, T.K., Sen, A.B., 1983. Susceptibility of Mastomys natalensis (GRA strain) to a subperiodic strain of human Brugia malayi. Ind. J. Med. Res. 77, 623–630. Murthy, P.K., Tyagi, K., Sen, A.B., 1986. Susceptibility of Macaca mulatta to a subperiodic strain of Brugia malayi. Ind. J. Parasitol. 10 (2), 189 – 192. Murthy, P.K., Tyagi, K., Chatterjee, R.K., 1990. Indian langur (Presbytis entellus) as experimental host of Brugia malayi infection. Curr. Sci. 59, 1236 – 1239. Nielson, K., Fogh, L., Anderson, S., 1974. Eosinophil response to migrating Ascaris suum larvae in normal and congenitally thymusless mice. Acta Pathol. Microbiol. Scand. 82, 919 – 920. Orihel, T.C., Pacheco, G., 1966. Brugia malayi in the Philippine macaque. J. Parasitol. 52, 394. Petranyi, G., Mieth, H., Leitner, I., 1975. Mastomys natalensis as an experimental host for Brugia malayi subperodic. SE Asian J. Trop. Med. Publ. Health 16, 328. Pollaco, S., Nicholas, W.L., Mitchell, G.F., Stewart, A.C., 1978. T-cell dependent collagenous encapsulating response in the mouse liver to Mesocestoides corti (cestoda). Int. J. Parasitol. 8, 457 – 462. Renoux, G., Renoux, M., 1980. The effects of sodium diethyldithiocarbamate, azathioprine, cyclophosphamide or hydrocortisone acetate administered along or in association for 4 weeks on the immune responses of Balb/c mice. Clin. Immunol. Immunopathol. 15, 23 – 32. Schacher, J.F., Sulahian, A., Edeson, J.F.B., 1969. Experimental lymphoedema in dogs infected with Brugia spp. Trans. R. Soc. Trop. Med. Hyg. 63, 682 – 684. Tyagi, K., Murthy, P.K., Chatterjee, R.K., 1996. Brugia malayi in Indian Leaf monkey (Presbytis entellus)—Response to repeated exposures of infective larvae. Curr. Sci. 70 (2), 164 – 167.
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