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Plasma testosterone in Trypanosoma congolense-and Trypanosoma brucei-infected West African dwarf rams
Animal Reproduction Science, 22 (1990) 21-26
21
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
P l a s m a T e s t o s t e r o n e in Trypanosoma congolenseand Trypanosoma brucei-Infected West African D w a r f Rams 0. ADEYEMO 1, A. OYEJIDE ~ and O. AGBEDANAa
Departments of Veterinary Anatomy, Veterinary Pathology ~ and Chemical Pathology 3, University o[ Ibadan, Ibadan (Nigeria) (Accepted 12 October 1989)
ABSTRACT Adeyemo, O., Oyejide, A. and Agbedana, 0., 1990. Plasma testosterone in Trypanosoma congolense- and Trypanosoma brucei-infected West African dwarf rams. Anim. Reprod. Sci., 22: 2126. To investigate the testicular endocrine changes associated with mixed trypanosome infection, rams of the West African dwarf (WAD) breed were inoculated with Trypanosoma congolense and T. brucei. Serum testosterone concentrations were determined weeks pre- and post-infection, and after subsequent treatment of rams with Berenil. Testosterone concentration (2.6_+ 0.2 ng/ml) showed a progressive decline from 5 weeks post-infection to 0.6_+ 0.1 ng/ml by the 10th week in the surviving rams. After Berenil treatment, testosterone level rose only slightly to 1.1 _+0.1 ng/ ml 5 weeks post-treatment. The study shows that testicular endocrine activity is altered during trypanosomiasis. The restoration of testicular endocrine function after recovery of rams from chronic mixed trypanosome infection is slow.
INTRODUCTION
Trypanosomiasis, a major livestock disease in the tsetse fly belt of Africa, is considered the most important limitation for livestock development in the area. Under field conditions, mixed infections of animals with different species of trypanosomes are more frequently encountered and may be more injurious than single infection. There are reports that lesions of trypanosomiasis occur in the reproductive system of the male animal; such lesions include testicular necrosis, calcification of seminiferous tubules and disturbed spermatogenesis in T. vivax-infected sheep and goats (Isoun and Anosa, 1974a) resulting in abnormal spermatozoa (Isoun and Anosa, 1974b). T. congolense infection also caused impaired spermatogenesis (Kaaya and Oduor-Okelo, 1980) as well as aspermic seminif0378-4320/90/$03.50
© 1990 Elsevier Science Publishers B.V.
22
O. ADEYEMO ET AL.
erous tubules and epididymides and desquamation of tubular germinal epithelia in the goat (Waidi et al., 1986). There is scanty information on the testicular endocrine response during trypanosomiasis. Plasma testosterone was depressed in goats infected with T. congolense (Waidi et al., 1986). In this study, the effect of mixed infection of T. brucei and T. congolense on the testis was assessed by the changes in plasma testosterone levels. MATERIALSAND METHODS
Animals Eighteen rams of the West African Dwarf (WAD) breed, locally raised, were purchased and kept in three equal groups in separate pens screened with flyproof wire gauze. They were aged 1.5-2 years, and were acclimatized for 3 weeks before infection with T. brucci 8/18 and T. congolense (untyped), obtained from the National Institute for Trypanosomiasis Research, Kaduna, and previously maintained in our laboratory by serial passages in rats. The rams were fed giant star grass (Cynodon plectostachyus) and legume (Centrosemapubescens) once daily, supplemented with concentrate at the rate of 0.4 kg/ram day- 1. Water was supplied ad libitum. Rectal temperature was recorded weekly. About 1 × 106 trypanosomes of each trypanosome species was inoculated into each ram via the jugular vein. Control rams were inoculated with 5.0 ml of saline.
Blood sampling Blood samples were collected from the animals by jugular venipuncture into heparinized tubes with the vacuum blood collecting system (Jintan Terumo Co. Ltd., Tokyo, Japan). 5 ml of blood were collected weekly before the sheep were infected, 1 ml daily from the day after infection for 1 week to establish infection, and subsequently, 5 ml once weekly. Parasitaemia was established by examining several fields of a blood smear under a microscope. The buffy coat technique was also used for the determination of parasitaemia (Murray et al., 1977). The remaining blood was centrifuged at 2500 rpm for 10 min to separate the plasma which was then stored at - 20 ° C until used for hormonal assay.
Treatment with diaminazene aceturate (Berenil) After 10 weeks of infection, animals that survived were treated with Berenil (Hoechst A.G., Germany) at the rate of 7 mg/kg body weight by intramuscular injection. After the treatment, blood was collected from the animals for another 6 weeks.
PLASMA TESTOSTERONE IN TRYPANOSOME-INFECTED RAMS
23
Radioimmunoassay of testosterone Plasma testosterone concentration was determined by radioimmunoassay as described by Adeyemo and Heath (1980) with some modifications. The standard curve was constructed by use of purified testosterone for radioimmunoassay (Sigma) at increasing concentrations from 5 pg to 200 pg per tube. Diethyl ether (BDH Chemicals Ltd., England, Analar grade, 3 ml) was used to extract 100/~l of plasma. The extraction recovery, determined by addition of 5000 cpm of radioactive testosterone to a plasma pool before extraction, was 98%. The antiserum to testosterone was raised in rabbit to testosterone-llcarboxymethyloxime-bovineserum albumin and used at a dilution which bound 33% of 3H-testosterone. It has a cross-reactivity of 3 and 30% with androstenedione and 5a-dihydrotestosterone (5~-DHT), respectively. (1, 2, 6, 73H)-Testosterone with specific activity of 110 Ci/mmol was purchased from Amersham International (Buckinghamshire, U.K. ). Dextran-coated charcoal was used to separate the unbound steroids from bound after the antigen-antibody reaction of the assay. Radioactive counting was done with a liquid scintillation spectrometer (Packard, model 3309). The sensitivity of the assay was 3 pg/ml and the intra- and inter-assay coefficients of variation were 5 and 8%, respectively.
Statistical analysis The Student's t test was used to determine the significance of the differences in the data obtained from the control and infected rams. RESULTS
Plasma testosterone Plasma testosterone concentration in the control rams remained within a range of 1-5.6 ng/ml with a mean and standard error of 2.6_+0.26 ng/ml throughout the experimental period. Our experience has shown that such low values of plasma testosterone are characteristic of indigenous rams in the tropical seasonal equatorial climate of the present study where the animals show no seasonality in breeding. There was no significant difference in the values between the control and treated animals up till 5 weeks post-infection, when a decline in the plasma testosterone occurred in the infected group (Fig. 1 ). Between the 5th and 10th weeks of infection, the testosterone levels were significantly lower in the infected rams (mean 0.6 _+0.1 ng/ml, P < 0.05 ) than in the controls. Episodic secretion of testosterone was not evident because of the long interval of sampling. However, occasionally high values were obtained (up to 5.6 ng/ml) in some individual control and experimental rams. This may represent sampling that coincided with episodic surge of testosterone secretion. Such
24
O. ADEYEMOET AL.
25
, - '
-
0 1 2 3 ~ 6 Weeks p r e - end post- infection
7
s
9
,0
Fig. 1. Plasma testosterone measured by radioimmunoassay in 6 rams injected with saline (solid line) and rams infected with T. brucei and T. congolense (broken line). The number of infected rams fell from 12 to 6 as mortality increased with the progress of the disease. Mean values of
testosterone with the standard error are presented. Arrow indicates day of inoculation. 3-
t-J
Lol.
0 ¸
Weeks p r e - ond post- treatment
Fig. 2. Plasma testosterone in 6 control rams (solid line) and in 5 rams previously infected with T. brucei and 7'. congolense (broken line) treated with Berenil.
values were usually mopped up when the mean values for the group were calculated for each week. Following Berenil treatment, plasma testosterone concentration remained low for 6 weeks. A slight increase was observed by the 5th week post-treatment to a mean of 1.1 _+0.1 ng/ml (Fig. 2). The values did not really rise to the normal levels during the periods of observation after Berenil treatment in spite of individual variation with some episodic elevated values. DISCUSSION
The reduction in plasma levels of testosterone suggests adverse effects of trypanosomiasis on the testicular steroidogenic cells, the interstitial cells of Leydig. This may be due to structural damage of the cells, the extent of which is to be determined in ultrastructural studies now under way. It has been postulated that testicular lesions described in infection with T.
PLASMA TESTOSTERONE IN TRYPANOSOME-INFECTED RAMS
25
brucei (Ikede, 1979) and T. congolense (Kaaya and Oduor-Okelo, 1980; Waidi et al., 1986) may be attributable to fever (Ikede and Losos, 1975; Kaaya et al., 1977; Griffin and Allonby, 1979). The hyperthermia may directly induce a decline in androgen secretion, since high temperatures have been known to affect both the A4 and A5 pathways of steroidogenesis (LeVier and Spaziani, 1968). The 3fl-hydroxysteroid dehydrogenase is particularly sensitive to high temperatures (Inano and Tamaoki, 1968). The possibility that pituitary damage during trypanosomiasis may result in testicular dysfunction has been suggested (Apted, 1970; Ikede and Losos, 1975). Such pituitary lesions may result in a decline in the release of interstitial cellstimulating hormone (ICSH or luteinizing hormone, LH) which may result in depressed function of the Leydig cells. Clinical evaluation showed that significantly body wasting was a common feature in the experimental animals during infection. This is a result of lipolysis inducible by chronic infections (Haslan, 1970). We were able to observe significant reduction in plasma levels ofphospholipids and cholesterol in rams after 5 weeks of mixed infection with T. congolense and T. brucei (Fig. 3 ). In conclusion, an implication of the reduced steroidogenic activity of the testis is a depression of the libido of the rams. The androgen-dependent activities of the testis and accessory glands would be disrupted or reduced and the quality of semen produced, both during and after a chronic infection, probably
E .40
-200E
,E,30-
- 150 ~E
eo-
-100 ~
10-
-50
'~.
r,
0
i
l
J
Weeks p r e - a n d post- Infection
Fig. 3. Plasma cholesterol (triangles) and phospholipids (circles) were estimated in 6 control rams (solid lines) and rams infected with T. brucei and T. congolense (broken lines). The numbers of surviving infected animals each week are indicated on the graph. Mean values with the standard error are presented.
26
o. ADEYEMOET AL.
altered. T h e effect of t r y p a n o s o m i a s i s on t h e libido a n d quality o f s e m e n of r a m s is u n d e r investigation. ACKNOWLEDGEMENTS T h e t e c h n i c a l a s s i s t a n c e of R o t i m i Anise is appreciated. We are grateful to the s t a f f of the U n i v e r s i t y of I b a d a n T e a c h i n g a n d R e s e a r c h F a r m for t h e care of the animals, G o d w i n N. N w a m a k o for p r e p a r i n g t h e g r a p h s a n d Arit E k w u r u k e for t y p i n g t h e m a n u s c r i p t .
REFERENCES Adeyemo, O. and Heath, E., 1980. Plasma progesterone concentration in Bos taurus and Bos indicus heifers. Theriogenology, 14: 411-420. Apted, P.I.C., 1970. Clinical manifestation and diagnosis of sleeping sickness. In: E.W. Mulligan and W.H. Potts (Editors), The African Trypanosomiasis. Allen and Unwin, London, pp. 661683. Griffin, L. and Allonby, E.W., 1979. Disease syndrome in sheep and goats naturally infected with Trypanosoma congolense. J. Comp. Pathol., 89: 457-484. Haslan, W.R., 1970. Gram-negative sepsis: another piece of the mosaic. New. Eng. J. Med., 282: 1127. Ikede, B.O., 1979. Genital lesions in experimental chronic Trypanosoma brucei in rams. Res. Vet. Sci., 26: 145-151. Ikede, B.O. and Losos, C.K., 1975. Pathogenesis of Trypanosoma brucei infection in sheep. J. Comp. Pathol., 85: 37-44. Inano, H. and Tamaoki, B., 1968. Effects of experimental bilateral cryptorchidism on testicular enzymes related to androgen formation. Endocrinology, 83: 1074-1082. Isoun, T.T. and Anosa, V.0., 1974a. Lesions in reproductive organs of sheep and goats experimentally infected with T. vivax. Tropenmed. Parasitol., 25: 469-475. Isoun, T.T. and Anosa, V.O., 1974b. The effect of experimental infection of Trypanosoma vivax on reproductive organ of sheep and goats. Niger. J. Anim. Prod., 1: 143-150. Kaaya, G.P. and Oduor-Okelo, D., 1980. The effect of Trypanosoma congolense infection on the testis and epididymis of the goat. Bull. Anita. Health Prod. Afr., 28: 1-5. Kaaya, G.P. Wingvat, G. and Johnson, L.W., 1977. Clinicopathological aspects of Trypanosoma congolense infection in goats. Bull. Anim. Health Prod. Afr., 25: 397-408. LeVier, R.R. and Spaziani, E., 1968. The influence of temperature on steroidogenesis in the rat testis. J. Exp. Zool., 169: 113-120. Murray, M., Murray, P.K. and McIntyre, W.I.M., 1977. An improved parasitological technique for the diagnosis of African trypanosomiasis. Trans. R. Soc. Trop. Med. Hyg., 71: 325. Waidi, E.N., Gombe, S. and Oduor°Okelo, D., 1986. Plasma testosterone in Typanosoma congolense-infected Toggernburg goats. Arch. Androl., 17: 9-17.
21
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
P l a s m a T e s t o s t e r o n e in Trypanosoma congolenseand Trypanosoma brucei-Infected West African D w a r f Rams 0. ADEYEMO 1, A. OYEJIDE ~ and O. AGBEDANAa
Departments of Veterinary Anatomy, Veterinary Pathology ~ and Chemical Pathology 3, University o[ Ibadan, Ibadan (Nigeria) (Accepted 12 October 1989)
ABSTRACT Adeyemo, O., Oyejide, A. and Agbedana, 0., 1990. Plasma testosterone in Trypanosoma congolense- and Trypanosoma brucei-infected West African dwarf rams. Anim. Reprod. Sci., 22: 2126. To investigate the testicular endocrine changes associated with mixed trypanosome infection, rams of the West African dwarf (WAD) breed were inoculated with Trypanosoma congolense and T. brucei. Serum testosterone concentrations were determined weeks pre- and post-infection, and after subsequent treatment of rams with Berenil. Testosterone concentration (2.6_+ 0.2 ng/ml) showed a progressive decline from 5 weeks post-infection to 0.6_+ 0.1 ng/ml by the 10th week in the surviving rams. After Berenil treatment, testosterone level rose only slightly to 1.1 _+0.1 ng/ ml 5 weeks post-treatment. The study shows that testicular endocrine activity is altered during trypanosomiasis. The restoration of testicular endocrine function after recovery of rams from chronic mixed trypanosome infection is slow.
INTRODUCTION
Trypanosomiasis, a major livestock disease in the tsetse fly belt of Africa, is considered the most important limitation for livestock development in the area. Under field conditions, mixed infections of animals with different species of trypanosomes are more frequently encountered and may be more injurious than single infection. There are reports that lesions of trypanosomiasis occur in the reproductive system of the male animal; such lesions include testicular necrosis, calcification of seminiferous tubules and disturbed spermatogenesis in T. vivax-infected sheep and goats (Isoun and Anosa, 1974a) resulting in abnormal spermatozoa (Isoun and Anosa, 1974b). T. congolense infection also caused impaired spermatogenesis (Kaaya and Oduor-Okelo, 1980) as well as aspermic seminif0378-4320/90/$03.50
© 1990 Elsevier Science Publishers B.V.
22
O. ADEYEMO ET AL.
erous tubules and epididymides and desquamation of tubular germinal epithelia in the goat (Waidi et al., 1986). There is scanty information on the testicular endocrine response during trypanosomiasis. Plasma testosterone was depressed in goats infected with T. congolense (Waidi et al., 1986). In this study, the effect of mixed infection of T. brucei and T. congolense on the testis was assessed by the changes in plasma testosterone levels. MATERIALSAND METHODS
Animals Eighteen rams of the West African Dwarf (WAD) breed, locally raised, were purchased and kept in three equal groups in separate pens screened with flyproof wire gauze. They were aged 1.5-2 years, and were acclimatized for 3 weeks before infection with T. brucci 8/18 and T. congolense (untyped), obtained from the National Institute for Trypanosomiasis Research, Kaduna, and previously maintained in our laboratory by serial passages in rats. The rams were fed giant star grass (Cynodon plectostachyus) and legume (Centrosemapubescens) once daily, supplemented with concentrate at the rate of 0.4 kg/ram day- 1. Water was supplied ad libitum. Rectal temperature was recorded weekly. About 1 × 106 trypanosomes of each trypanosome species was inoculated into each ram via the jugular vein. Control rams were inoculated with 5.0 ml of saline.
Blood sampling Blood samples were collected from the animals by jugular venipuncture into heparinized tubes with the vacuum blood collecting system (Jintan Terumo Co. Ltd., Tokyo, Japan). 5 ml of blood were collected weekly before the sheep were infected, 1 ml daily from the day after infection for 1 week to establish infection, and subsequently, 5 ml once weekly. Parasitaemia was established by examining several fields of a blood smear under a microscope. The buffy coat technique was also used for the determination of parasitaemia (Murray et al., 1977). The remaining blood was centrifuged at 2500 rpm for 10 min to separate the plasma which was then stored at - 20 ° C until used for hormonal assay.
Treatment with diaminazene aceturate (Berenil) After 10 weeks of infection, animals that survived were treated with Berenil (Hoechst A.G., Germany) at the rate of 7 mg/kg body weight by intramuscular injection. After the treatment, blood was collected from the animals for another 6 weeks.
PLASMA TESTOSTERONE IN TRYPANOSOME-INFECTED RAMS
23
Radioimmunoassay of testosterone Plasma testosterone concentration was determined by radioimmunoassay as described by Adeyemo and Heath (1980) with some modifications. The standard curve was constructed by use of purified testosterone for radioimmunoassay (Sigma) at increasing concentrations from 5 pg to 200 pg per tube. Diethyl ether (BDH Chemicals Ltd., England, Analar grade, 3 ml) was used to extract 100/~l of plasma. The extraction recovery, determined by addition of 5000 cpm of radioactive testosterone to a plasma pool before extraction, was 98%. The antiserum to testosterone was raised in rabbit to testosterone-llcarboxymethyloxime-bovineserum albumin and used at a dilution which bound 33% of 3H-testosterone. It has a cross-reactivity of 3 and 30% with androstenedione and 5a-dihydrotestosterone (5~-DHT), respectively. (1, 2, 6, 73H)-Testosterone with specific activity of 110 Ci/mmol was purchased from Amersham International (Buckinghamshire, U.K. ). Dextran-coated charcoal was used to separate the unbound steroids from bound after the antigen-antibody reaction of the assay. Radioactive counting was done with a liquid scintillation spectrometer (Packard, model 3309). The sensitivity of the assay was 3 pg/ml and the intra- and inter-assay coefficients of variation were 5 and 8%, respectively.
Statistical analysis The Student's t test was used to determine the significance of the differences in the data obtained from the control and infected rams. RESULTS
Plasma testosterone Plasma testosterone concentration in the control rams remained within a range of 1-5.6 ng/ml with a mean and standard error of 2.6_+0.26 ng/ml throughout the experimental period. Our experience has shown that such low values of plasma testosterone are characteristic of indigenous rams in the tropical seasonal equatorial climate of the present study where the animals show no seasonality in breeding. There was no significant difference in the values between the control and treated animals up till 5 weeks post-infection, when a decline in the plasma testosterone occurred in the infected group (Fig. 1 ). Between the 5th and 10th weeks of infection, the testosterone levels were significantly lower in the infected rams (mean 0.6 _+0.1 ng/ml, P < 0.05 ) than in the controls. Episodic secretion of testosterone was not evident because of the long interval of sampling. However, occasionally high values were obtained (up to 5.6 ng/ml) in some individual control and experimental rams. This may represent sampling that coincided with episodic surge of testosterone secretion. Such
24
O. ADEYEMOET AL.
25
, - '
-
0 1 2 3 ~ 6 Weeks p r e - end post- infection
7
s
9
,0
Fig. 1. Plasma testosterone measured by radioimmunoassay in 6 rams injected with saline (solid line) and rams infected with T. brucei and T. congolense (broken line). The number of infected rams fell from 12 to 6 as mortality increased with the progress of the disease. Mean values of
testosterone with the standard error are presented. Arrow indicates day of inoculation. 3-
t-J
Lol.
0 ¸
Weeks p r e - ond post- treatment
Fig. 2. Plasma testosterone in 6 control rams (solid line) and in 5 rams previously infected with T. brucei and 7'. congolense (broken line) treated with Berenil.
values were usually mopped up when the mean values for the group were calculated for each week. Following Berenil treatment, plasma testosterone concentration remained low for 6 weeks. A slight increase was observed by the 5th week post-treatment to a mean of 1.1 _+0.1 ng/ml (Fig. 2). The values did not really rise to the normal levels during the periods of observation after Berenil treatment in spite of individual variation with some episodic elevated values. DISCUSSION
The reduction in plasma levels of testosterone suggests adverse effects of trypanosomiasis on the testicular steroidogenic cells, the interstitial cells of Leydig. This may be due to structural damage of the cells, the extent of which is to be determined in ultrastructural studies now under way. It has been postulated that testicular lesions described in infection with T.
PLASMA TESTOSTERONE IN TRYPANOSOME-INFECTED RAMS
25
brucei (Ikede, 1979) and T. congolense (Kaaya and Oduor-Okelo, 1980; Waidi et al., 1986) may be attributable to fever (Ikede and Losos, 1975; Kaaya et al., 1977; Griffin and Allonby, 1979). The hyperthermia may directly induce a decline in androgen secretion, since high temperatures have been known to affect both the A4 and A5 pathways of steroidogenesis (LeVier and Spaziani, 1968). The 3fl-hydroxysteroid dehydrogenase is particularly sensitive to high temperatures (Inano and Tamaoki, 1968). The possibility that pituitary damage during trypanosomiasis may result in testicular dysfunction has been suggested (Apted, 1970; Ikede and Losos, 1975). Such pituitary lesions may result in a decline in the release of interstitial cellstimulating hormone (ICSH or luteinizing hormone, LH) which may result in depressed function of the Leydig cells. Clinical evaluation showed that significantly body wasting was a common feature in the experimental animals during infection. This is a result of lipolysis inducible by chronic infections (Haslan, 1970). We were able to observe significant reduction in plasma levels ofphospholipids and cholesterol in rams after 5 weeks of mixed infection with T. congolense and T. brucei (Fig. 3 ). In conclusion, an implication of the reduced steroidogenic activity of the testis is a depression of the libido of the rams. The androgen-dependent activities of the testis and accessory glands would be disrupted or reduced and the quality of semen produced, both during and after a chronic infection, probably
E .40
-200E
,E,30-
- 150 ~E
eo-
-100 ~
10-
-50
'~.
r,
0
i
l
J
Weeks p r e - a n d post- Infection
Fig. 3. Plasma cholesterol (triangles) and phospholipids (circles) were estimated in 6 control rams (solid lines) and rams infected with T. brucei and T. congolense (broken lines). The numbers of surviving infected animals each week are indicated on the graph. Mean values with the standard error are presented.
26
o. ADEYEMOET AL.
altered. T h e effect of t r y p a n o s o m i a s i s on t h e libido a n d quality o f s e m e n of r a m s is u n d e r investigation. ACKNOWLEDGEMENTS T h e t e c h n i c a l a s s i s t a n c e of R o t i m i Anise is appreciated. We are grateful to the s t a f f of the U n i v e r s i t y of I b a d a n T e a c h i n g a n d R e s e a r c h F a r m for t h e care of the animals, G o d w i n N. N w a m a k o for p r e p a r i n g t h e g r a p h s a n d Arit E k w u r u k e for t y p i n g t h e m a n u s c r i p t .
REFERENCES Adeyemo, O. and Heath, E., 1980. Plasma progesterone concentration in Bos taurus and Bos indicus heifers. Theriogenology, 14: 411-420. Apted, P.I.C., 1970. Clinical manifestation and diagnosis of sleeping sickness. In: E.W. Mulligan and W.H. Potts (Editors), The African Trypanosomiasis. Allen and Unwin, London, pp. 661683. Griffin, L. and Allonby, E.W., 1979. Disease syndrome in sheep and goats naturally infected with Trypanosoma congolense. J. Comp. Pathol., 89: 457-484. Haslan, W.R., 1970. Gram-negative sepsis: another piece of the mosaic. New. Eng. J. Med., 282: 1127. Ikede, B.O., 1979. Genital lesions in experimental chronic Trypanosoma brucei in rams. Res. Vet. Sci., 26: 145-151. Ikede, B.O. and Losos, C.K., 1975. Pathogenesis of Trypanosoma brucei infection in sheep. J. Comp. Pathol., 85: 37-44. Inano, H. and Tamaoki, B., 1968. Effects of experimental bilateral cryptorchidism on testicular enzymes related to androgen formation. Endocrinology, 83: 1074-1082. Isoun, T.T. and Anosa, V.0., 1974a. Lesions in reproductive organs of sheep and goats experimentally infected with T. vivax. Tropenmed. Parasitol., 25: 469-475. Isoun, T.T. and Anosa, V.O., 1974b. The effect of experimental infection of Trypanosoma vivax on reproductive organ of sheep and goats. Niger. J. Anim. Prod., 1: 143-150. Kaaya, G.P. and Oduor-Okelo, D., 1980. The effect of Trypanosoma congolense infection on the testis and epididymis of the goat. Bull. Anita. Health Prod. Afr., 28: 1-5. Kaaya, G.P. Wingvat, G. and Johnson, L.W., 1977. Clinicopathological aspects of Trypanosoma congolense infection in goats. Bull. Anim. Health Prod. Afr., 25: 397-408. LeVier, R.R. and Spaziani, E., 1968. The influence of temperature on steroidogenesis in the rat testis. J. Exp. Zool., 169: 113-120. Murray, M., Murray, P.K. and McIntyre, W.I.M., 1977. An improved parasitological technique for the diagnosis of African trypanosomiasis. Trans. R. Soc. Trop. Med. Hyg., 71: 325. Waidi, E.N., Gombe, S. and Oduor°Okelo, D., 1986. Plasma testosterone in Typanosoma congolense-infected Toggernburg goats. Arch. Androl., 17: 9-17.